Posted: Jan Wed 16, pm. Hi 2N is a NPN, silicon, power transistor. Posted: Jan Thu 17, am. Hello yup thats the beast good photo of it! If i knew how to post photos and resize i would. Dont even know how to link.. Maybe one day.. I will have to try one i got a science fair crystal kit new in the box never opened!
Shop Mit Radlab Complete Set Vol 16 Microwave Mixers 1948
May be fun works got me busy! I used one of those noise generators as the mixer in my first Mhz converter in the early 60's. And that was after selecting the best diode out of about Posted: Jan Thu 17, pm. Microwave mixer diodes are probably not the best choice for a crystal radio since they're VERY easily damaged by stray electrical charges. Special test sets were used to check them since a standard ohmmeter would blow them. Maybe the ones I have in my collection are bad, but when I checked them a few years ago they showed a forward conduction voltage of around.
That made me think they were possibly germanium. I also read that they were point-contact type diodes. I have never heard of a point-contact silicon diode and all the point-contact diodes I am aware of are germanium. Maybe time for some person who is into minerals to disect one and see what they are really made of? Hi Curt and I have discussing 1N23 diodes by email. Believe they are germanium although books mention silicon. The diodes do make good crystal sets.
They have a low voltage drop and have a lot of leakage unlike silicon diodes. Diodes were classified during WW2. So far I have not found complete data on 1N21, 1N22 and 1N23 diodes. There is a catswhisker inside that cartridge!! The voltage drop characteristics of point contact diodes are much like modern Shottky diodes. There is an entire volume Vol. Vol 16 has lots of data on 1N21 thru 1N Vol 15 which I don't have is supposed to have more data on crystals used for IF detection, etc such as the 1N As of when Vol 16 was published, it says: "In practice, the crystals used for microwave work are usually made of silicon These books are still available in most engineering libraries, many larger public libraries, and of course, Amazon.
Page 1 of 2. Previous topic Next topic. Norm Leal. Post subject: Posted: Jan Sat 12, pm. Post subject: Posted: Jan Sun 13, pm.
- Rubber compounding : chemistry and applications?
- Share This!
- Oral History Interviews.
Peter Bertini. It was so trivial as far as I was concerned. I skipped the second term. Well Bob, if you got 99, you had learned a lot of physics. Had you learned that just on your own? I had been heavily into photography for years and I knew a lot of optics, geometrical optics, because I was also building a telescope, grinding a mirror, learned about the Foucault knife edge test, things like that and so forth.
And I knew about three different kinds of eyepieces — Ramsden, Newton, and what's the other one? I forget. So I had done all these things, and so that the physics course was absolutely trivial. The 99 was because of the question I missed, was to do with a question of who saw the apple fall. And I never read much of that stuff, so it was multiple choice and I chose the one, I think I chose Galileo instead of Newton. And ever since I've not been one for saying who did what. I say that's a part of social science and not physics in a sense. Well, we're now sitting here and we're going to try to understand what Bob Pound did as we go on.
So okay, you went from high school to the University of Buffalo. Was that choice simply because it was nearby? It was relatively economic I should say, because I never thought much about going somewhere else, and in many ways I think if I had known enough about Rochester at that time which was quite, fairly nearby, I might have been inclined, because they had a wonderful physics department then with L.
Dubridge and Vicky Weisskopf and so forth. But — and they were building a cyclotron with Van Voorhis. But — our university, my father taught in the math department, but he actually taught all the analytical mathematics used by the physicists, so he and then I, knew many of the young people who had gone through as physics students there. And I had two different scholarships — a New York State scholarship. That year was in fact, this high school I went to called Amherst Central High School, it had been founded in I think or '30, and ours was the first class that won New York State scholarships.
I think the number of New York State scholarships was equal with the number of something or other, representatives from the county to the state legislature. And that was the first year any of them had been won by the Amherst Central High School, but there were six of the forty in that school that year. Previously they were won mostly in Buffalo high schools as, for example, by my oldest sister. And then it also was announced at the graduation that I had been awarded an Erie County Supervisors Scholarship to the University of Buffalo, which was a full tuition.
In those days tuition was the only thing you got covered with scholarships, so I had that plus the hundred dollars a year for the two years — it was only two years — I'm sorry, full tuition for two years, and in the last two years, of which I only spent a year and a half, I earned my keep by being a teaching assistant. I was so-called senior assistant. It was rather spotty I'd say in a sense. I mean there were some very, very dedicated teaching people, but I would say that, for example, a man that was my brother-in-law came there from Yale in the fall of — sorry — in the summer of , and in the fall of he taught a course called quantum mechanics, but he was really an experimental nuclear physicist and his quantum mechanics was what he'd learned from [Henry] Marganau at Yale.
And I didn't learn much from it. I took that course. And but my actual supervisor, advisor and so forth was a man named L. Grant Hector [spelling? Grant Hector had been a student of [A. In fact the predecessor to I. In fact Rabi once told me that he took over Hector's apparatus when he became Wills' graduate student. But then Rabi said the trouble was that he, Rabi, was so smart that he didn't ever use anything.
He invented a way of doing what he was to do for his thesis without building anything. So then he said thus he regrets that he never learned any experimental physics as a result. I guess I can't tell you much about Rabi, but —. Well, that's a true story. Rabi was I think fundamentally lazy, and if he could not find a simple way of doing something he probably didn't do it, and he kept trying until he did.
I asked you the question about your undergraduate education because I was setting you up a bit. You have the distinction of being a full professor at Harvard and have an illustrious career and you only have a bachelor's degree. That's your only formal degree. And that was in three and a half years instead of four, because I left early when I was offered an opportunity to go into defense activity. I didn't have quite enough credit to graduate, but Hector stirred up a couple of extra semester hours credit for my tutorial work so that I could make the graduation requirement.
In the tutorial program, I had been pursuing a project in dielectric susceptibilities that took most of my time for the last two years, building electronic apparatus for example. Now how was it that a young fellow with a bachelor's degree, how did you get attracted to or how did you get an offer to get into defense work? And where did you go from Buffalo? Well, of course what was going on then was that the war was getting intense in Europe and our Selective Service began. I had to register for Selective Service October 16, , and it was clear that our future as going to graduate school and going on in science was very prejudiced by all this.
And so when my brother-in-law, Howard Schultz, who became a professor at Yale after the war but had got his Ph. He was also being recruited at the same time, in competition, to a company called the Submarine Signal Company in Boston, in which my other brother-in-law Harold Hart was the head of the radar department. They had developed a radar department entirely on their own starting in , which was long before anybody else. And H. Hart had also been a graduate student at Yale and had worked on his thesis work with a man named L.
McKeehan, who was into magnetostriction which was used in sonar. I'm not sure. M-c-k I think. And he was a consultant to this Submarine Signal Company. And so Harold spent his summers working for them, and they talked him into coming full time around , and he took over and he gave up his thesis work at Yale.
Howard Schultz had done his thesis work at Yale with — what's his name? With Ernie Pollard. They shared in the building of the first Yale cyclotron. So both my sisters were married to physicists who had also graduated from the University of Buffalo. Well, they were developing it when I came. I came down for an interview in November or December to see about what this — and that's when I first saw radar running.
And Harold built this centimeter radar and it used a Western Electric vacuum tube called the It was called a doorknob tube and that was nominally a volt vacuum tube, but they were hitting it with volt pulses and making pulse r-b signals. And the people who investigated organizations trying to develop radar at that time wanted to know how come they were the only company that was playing with pulsed radar at that time. And the reason was, they were doing it by pure analogy to their business, which was sonar. And they had been founded during World War I under Fessenden patents, I used to hear — I'm not sure about that — for developing sonar.
They were founded, I believe, by MIT people actually. And they were very proud of their economic success because they survived during the big Depression by developing what they called Fathometers and renting them or leasing them to the fishing fleets here in Boston which went out to find fishes. And they thought very lowly of Raytheon, which was a more or less defunct company at the time. The only thing they did then was to build vacuum tubes mostly for ham radio and such.
You didn't make it clear. You went from your baccalaureate at Buffalo to defense work where? Well, I started there on February 1st, and in the summer of '41 — well, at the same time I was living, I shared living with my sister Kathleen and brother-in-law, Howard Schultz, who was then at Radiation Lab, so I was quite aware of that combination of things, and the Submarine Signal Company was closely involved with advice and help from Radiation Lab, although they were actually ahead of Radiation Lab in the beginning. In fact we built a pulsar for the magnetron. Semmes, which was the then sort of sailing test bed for the Navy.
The Radiation Lab ended up using it for a radar test bed in later times. Well, in the summer of '41 after I'd been there six or seven months it became clear that Radiation Lab was going to bypass the whole business. To be in research in a small company like that when there were three of us involved in that program didn't strike me as viable. I saw that the company would end up in production of some kind, engineering, and I wasn't inclined in that direction. So I went over there and spent many weeks.
Actually I built the first electrostatically deflected PPI, Plan Precision Indicator , which is the sweeping kind of radar indicator, and Charles Sherwin was building one which was a magnetic type which is what mostly ended up getting used. This was a group that was headed by Bob Bacher, and a man named Ted Seller was the actual head of that group at the time. So I was in conventional electronics, because that was my big experience from my background.
And I could see that if I had hung on for a few more weeks before going to Boston, I probably would have ended up directly at Radiation Lab. So I started petitioning, I started to see if I could make this switch. And I would get in touch with F. Wheeler Loomis, who was the associate director, for personnel particularly, and he finally told me that he'd like to offer me a position but he couldn't because with defense deferment I would have to get a release from the company that had got me deferred from the Selective Service.
So I spent some time, in the fall of , this was before Pearl Harbor, they put the condition that they would give me the release if I would finish the actual model of their centimeter radar that they wanted to have as a demonstration of what they had done. It had been working but it was not fully assembled and so forth. We had a pair of big horns on the roof that were steerable. So in fact I went through that and I did that. Finally I got ill in early March ' And when I got strong enough to go back I went in to see the vice president, a man named Fay Charles and told him this thing was working and finished and so forth, and finally, they signed my release.
So I became one of his first tools in the microwave components group in March, So I think of myself [as] having been at Radiation Lab before that, you see, because of this visiting and other close contacts. I'm going to switch this tape, because it's almost done. There were a lot of very well established and rather eminent people at the Radiation Lab, and you came in with a bachelor's degree. Were you treated well? Oh yes. I would say I was treated well. Of course I knew that having come from a local environment I didn't have the advantages that some of the people coming from elsewhere economically in the beginning did, because I know that my brother-in-law for example was given a salary plus living expenses so that it almost doubled what he was getting as an instructor in college, but of course instructors didn't do very well in those days.
Oh no, no. As a mat — Well, you see I was in Zacharias's group and I was one of his — and within a few weeks I got established as sort of one of his favorite subgroup. I had a subgroup that I organized and although that came along when I was in charge of mixers, but I and a man named Louis Smullin were particularly involved in what they call mixers and duplexers, which was the front end of radars. And we had a major problem, which was, because, in the field when colleagues went out to look at Radiation Lab — developed radars they would find they weren't working well at all because the military had no clue about the fact that crystals could always get burned out even at the first turn-on, and so they were operating tens of db or more below their expected receiving.
But you see, they would see local echoes perfectly all right because the inverse fourth power that applies in radar. That meant that you didn't notice the loss particularly on local things but you really needed the sensitivity for remote. Let me ask this. In , '42, when the Rad Lab was getting started, how much was known about getting power around a circuit at microwave frequencies? Well, there were people who knew about, say, waveguides but they were mostly academics that had never done anything with them. Page for example at Yale had written some articles describing waveguides.
Because I know that my other brother-in-law, Harold Hart, told me that on his oral exam there he was asked a question about that and he doubted it. But the big thing at Rad Lab was that everybody was trained, got to know more about microwave technology, because of the wonderful series of lectures by W. Bill Hansen came every week up [from] Garden City, Long Island, the Sperry Gyroscope Company, where he was full time and gave these once a week lectures which got annotated, got transcribed.
Who did that? I keep forgetting. It was one of his cohorts from Stanford who served as the Boswell for those notes, and I still have copies. No, no, no. Packard was a graduate student after the war and he only got there late. No, no, this was a — I can see him but I can't remember his name. Names are harder to get as you go along. But things like the Magic T and various components that went into a microwave system, were those invented at the Rad Lab?
Well, the Magic T is an example of a disputable issue, because Bob Dicke was the one that really realized the full properties of the Magic T if it were properly matched to a system so that all four arms were equivalent. However, there was a patent issue that came up about that. And Dicke had a patent application from Radiation Lab for it, and there was a man — now another name I've forgotten — at the Bell Labs, who had written a book on microwave hybrid circuits. Not a book — I'm sorry, a memorandum for file is what they call it at Bell Labs, and we had access to much. All that stuff came in through our documents office.
And this was — and hybrid circuits were the low frequency equivalent to what became a Magic T. And he was discussing how to make them in microwaves correctness and waveguides for example. And it was what we ended up calling a rat ring, a rat race with four arms going into a ring of waveguide, and if you put them at quarter wave spacing and halfway and so forth you got the exact same behavior as you got with a Magic T, although that was before there was a Magic T.
But then that paper went on to describe that you could put a waveguide on the side which you called a series junction or on the broad side of the waveguide, or the narrow side and call it the equivalent of a parallel junction. But the difference would be that you'd moved a quarter wavelength to go from one to the other, because then the phase issues were the same. But then he had a picture in his report showing that you could even put two of them in the same place.
But that picture, which was a Magic T by everyone's understanding later, was a picture of what you might have as a pair of junctions on the ring — not a recognition that in itself it was just what he was looking for. And yet that picture won the patent issue, so he got the patent on, Bell Labs got the patent on that thing. One more question in this same vein. To what extent were you guided by any theory that say Julian Schwinger was doing? Very little, because in my design of mixers — Julian came back to the Radiation Lab only late, you know.
He wasn't there the whole time at all. That was Lou Smullin and I who were doing this. And Julian thought about it and the next morning proposed a way to redesign the resonator for the TR box that might reduce this feedthrough. And we lost many weeks building this thing this way and it turned out it didn't make any difference. It turned out that what he proposed had to be — it weakened the transmission but it also weakened the coupling in such a way that when you adjusted it with the right way to get back where you had to be, it had the same feedthrough.
So that was the early time, and then he went off to Purdue, where he taught for some time. And then when things got tight he came back to Radiation Lab. And then he — oh, what I was going to say is, I designed a mixer in which I had to have coupling from the — you have to have the local oscillator feeding into the mixer, but not interrupting the flow of the weak signal. And I did, instead of cut and try as we usually did with these things, I tried to use Schwinger's network theory to design this exactly, and it took me days of hand calculations to do, to get the equivalent circuits to all these corners and things that he — and when I got done it really was much easier to have done it just by cut and try.
Not really. I had two or three members in my subgroup as it was called, but I shared an office there with the people who were in charge of the crystal development, namely Henry Torrey and Charlie Whitmer, and so we were very close friends and that's how we all of course, Henry and I got together with Purcell on NMR? It was a different environment in the sense there was, everything was more, I guess everything was classified, there was security visible.
Did that bother people used to freedom in the academic world? Well, before I answer that question I might tell you how I made my situation with Zacharias and company, because I was assigned the job of designing or finding out — I'm going to start over again. The lab had decided that they couldn't use bead-supported co-axial lines anymore; they wanted to use stub-supported; stub-supported lines, which means you put a little quarter wave long stub that's short circuited at the end to support the inner conductor, and it doesn't have all this reflection problem of the former plastic beads.
But it has to be an effective quarter wave, and at 10 centimeter wavelength, which is what we were using then, there were three sub-bands: 9. Smith charts — and solve the problem as to how it worked. And it turned out that that became the way to supplement microwave things. And in fact I can show you that. Let's see. And this thing is B there's a patent applied for by the Army Signal Corp.
Well, what we had to do was, I had to write a report for the Radiation Lab. And Zacharias, in order to get this report officially approved, and I had to go and see Sam Goudsmit, who was in charge of these things at that time. And this was in the spring of And I knew the name of Goudsmit at the time, coming from where I did. Because what made my status in the — that was about two weeks after I first came permanently into the microwave business.
All right, back to my question. Did the security issues and the classification and all bother people? Well, yeah. Of course it did to the extent that Ajax Allen got shot in the stomach by the security guards. Well, it was — after one of our Monday night seminars we had regularly, and Allen decided to go back to the lab for something. He was actually in charge of buildings and grounds for the Radiation Lab, and he was challenged at the guard's gate, and he saluted them thinking that they would recognize him and he just drove on, so they shot him.
And he had to go to the B to the hospital with surgery for gunshot wounds in the stomach. No, that was around or Early we had a simple kind of guarding system with retired Cambridge policemen and such people, but after Pearl Harbor then there was an Army group that came with their riot guns and everything and they stood at all the places. I might say that when I got interviewed for the Society of Fellows, the rather eccentric Englishman, Arthur Darby Nock, who was then acting chairman always used to tell people as to how he went down to the MIT secret laboratory and to see Rabi, who was one of my sponsors at the time, and he said he got — he was so impressed, because he got past the guards there.
You know, he got escorted through the guards and so he was quite impressed with that. How much were you aware and others at the Rad Lab in general about what was going on at Los Alamos? Rather little in the sense of detail, but rather thoroughly in view of who was involved and that they were into this particular aspect of nuclear physics.
Because of course many of our colleagues were recruited away, and people don't generally realize how many of all the important people were at Radiation Lab in the beginning, including E. Lawrence and including Backer and we referred to it as Shangri La. Bethe, and Ken Bainbridge in particular. He became, you know he was the head of the Trinity Test, and so he, I knew him fairly well from the early times, but it was March that he was recruited out to Los Alamos.
He was the first person actually to have been recruited to Radiation Lab in Because E. Lawrence was a major recruiter for the Radiation Lab, and he came — but that's because he was a friend of Alfred Loomis, who was the member of the — what do you call? And he chaired the microwave subcommittee, and Lawrence knew him very well because with Alfred Loomis' interest in technology he had become the financial source for Lawrence and his cyclotrons. He got his banker friends to help support the cyclotron. So then Lawrence came here to Harvard apparently, as Ken told me, Ken Bainbridge told me, and asked him to come over and walk in the yard where there would be fewer ears close by and talked him into taking leave and coming to MIT which was just founding the Radiation Lab.
So he was the very first. He was number one. Well, when the war ended, there was a Time magazine that was scheduled to have the radar story as the cover. Did the people at the Radiation Lab feel that they had really been overlooked in terms of the importance of the work that they had done? I think they were also overcome with excitement over what had happened at Los Alamos in fact, but they knew perfectly well that what they — it used to be said I guess you've read in a number of places that they said that the bomb ended the war but the radar won the war.
Well, it was of course the involvement, it was of course the intensity of having to keep going at things and knowing it was going to have some value — plus the fact of being involved with all those, say 50 percent of the distinguished scientists or physicists in the country. And for example it wasn't just physicists either; I spent the evening the other day, well, I spent lunch on Tuesday entirely with Paul Samuelson.
You wouldn't expect that he was a member of the Radiation Lab, which he was. He's the economist at MIT. And the reason that he got to Radiation Lab was that he was a junior fellow in the Society of Fellows, and there were two other distinguished junior fellows who played very important roles at Radiation Lab. One was Ivan Getting and the other was Dave Griggs, and they were close, they were contemporary colleagues. They were all junior fellows at that same time that Paul Samuelson was, so they put him into — I can't remember what group he got into.
But of course Paul had that particular interest in physics as much. Two more questions on the Radiation Lab. Were you at ease with the whole writing effort at the end when all of you folks were writing these books? By the way, not all were in the writing operation. I wouldn't know what you mean by being at ease, because we — I didn't like to spend my time while I was down there sitting at a desk writing, because some of my apparatus was being, had been hijacked into the continuing Research Laboratory of Electronics RLE.
And in fact, following a suggestion I had made, Al Hill and Arthur Roberts and somebody else were using it to look for the hyperfine structure in absorption of cesium in the microwave stabilizer. So I would go on kibitz and look at what they were doing whilst I was supposed to be writing the books. And seeing all these people getting on with their lives, and here I was stuck to have to sit down and write this book.
Well, my question was — my understanding is that this writing effort was launched by Rabi, who said something to the effect that we didn't write it up all of this knowledge would go to Bell Labs, and he felt that —. Well, did he put it that way? I see.
The MIT Rad Lab Series
I hadn't known about the worrying about Bell Labs, but I thought he thought it would be lost, but never mind. Oh, I think that they recognized that there are quite a lot of — that the changes and advances in technology of that kind was very, very significant and it shouldn't be lost and we should probably gain the credit for it if that's — I think anybody was taking the credit for it, but I mean you know, people like Brit Chance who had done some great things in precision measurement techniques and so forth, these were things that had to be preserved.
And of course my, I have that book I wrote. I don't know if you've ever seen it, but is this the one? And there is the most sophisticated microwave mixer, which has three Magic Ts. That was inspired jointly between me, Bob Dicke and Ed Purcell. Well, it's worse than that.
This is the rough B this is die casting which we had made by Yale and Town, who were the people who make Yale locks down in Connecticut. But the first model, the test model of this was made by a very distinguished local flute maker.
- Contemporary Aristotelian Metaphysics.
- Navigation menu!
- You are here.
William S. Haines, yes. And I went down — we had a man named Jules Simmons who took charge of our getting things made and getting things done, and he took me over to William S. Haines, which used to be over Mass Station in Boston, and I went over there whilst they were machining this thing out of solid brass.
And they were doing a beautiful job. And they such — a wonderful thing. And they had just — a man at Case, a University in Cleveland, a mathematician had just died and it was announced in the newspapers that he had a collection of Haines flutes, platinum Haines flutes, and they said they hated platinum because it's awful stuff to work with. But they had one man working on a desk repairing flutes, and everybody else was doing our kind of thing, and so they said would I like to try to play a flute. And he was also, they were also making at the time tapered hexagonal — they had metal violin bows they were making, and they were made out of tapered aluminum, hexagonal aluminum, the backing of the bow.
And I said how did they make that? Where did they get that from? They said well, they tried all the aluminum makers and nobody would do it so they had to do it themselves. One last question about — When you closed shop at the Radiation Lab, you were certainly aware that a lot of new physical techniques had suddenly become available.
As you looked ahead was there a great sense of sort of anticipation as to what would be possible in physics following the war years? Well, I think most people thought more in terms of what you could do in the way of accelerators with our microwave technology, and I of course was looking for a way to do something in physics with my limited background.
I hated glass blowing among other things, and my mentor Hector for example spent a long time trying to make a vacuum gauge out of a receiving tube, type 59 I think it was, and never succeeded in sticking a pipe onto the side of the vacuum tube glass. And that's because these glasses are not compatible. I mean, you never get glasses with the same expansion coefficient. But I did think, among other things, that microwave spectroscopy was going to be of an interest. And in fact I had been trying to relearn some physics or learn some physics I had never fully learned, and I got the little book of Herzberg on atomic physics, on atomic spectroscopy, and there was a footnote about the fine structure constant of hydrogen, the wave number of which it said had been measured as.
I once mentioned that to Herzberg when I met him in Toronto at one time, and he said, Lamb said that's where he found [out] about it too. Yeah, I was saying something about the ammonia microwave absorption which had been well known from Leeton and Williams from the early thirties, and they had done marvelous things in that they built their own magnetrons to do that with and so forth. And I was quite aware of that, plus the water vapor absorption. But my particular interest at the time was that I foresaw building an atomic clock, because my — one of the things I was most celebrated for at Radiation Lab was developing the technique of frequency stabilization, and all kinds of the early microwave spectroscopists referred to the Pound stabilizer as being what they used to get good signal sources and so forth.
And so I, but I had — in fact in my interview with the Society of Fellows proposed using an atomic absorption line like ammonia or whatever to stabilize instead of a cavity which I was using then, because that's not absolute, whereas this other one — And I foresaw using that to measure the difference in different kinds of timescales, and thus I was thinking in terms of — I had been influenced by reading an article about E.
Milne who had some proposals of kinematic and dynamical timescales by which the difference in the two timescales should change by about one over the age of the universe per year, which meant in those days about a part in 10 10 per year if those two timescales really existed, one based on atomic spectra and the other on gravitation or whatever. So that was one of the things that I had the greatest enthusiasm. And then of course what came along was this idea of Purcell's of looking for the absorption of protons. All right, before we get to that, let's go back.
You almost provided the perfect springboard. How was it that you got the attention of the Society of Fellows and were asked to become one? You were doing classified work. How did they know about you? Of course there were these other people there. Well, you know the Society of Fellows functions only by nomination by sponsors, and the person that first told me that — My colleagues knew my ridiculous status of never having gone to graduate school, and but it was Al Hill that first mentioned it to me. He said that he had developed the plan of having me, nominating me to the Society of Fellows at Harvard.
I didn't know anything about it then, but we had several Radiation Lab people, as I mentioned — Paul Samuelson whom I didn't know then, but the one I knew best was Ivan Getting, and he had been a junior fellow for six years I think, which was illegal. I mean six years was the maximum, but the one that was illegal was Dave Griggs, who had been seven years, because he spent one of those years in the hospital. But he got into Radiation Lab because he flew a plane.
Goetting got him to fly his plane as a target plane for testing the early radar, so that's — and then he ended up being part of the Radiation Lab. Of course he got a bad name in the long run for his testimony against Oppenheimer. Dave Griggs. He was a geophysicist while he was a junior fellow. He was using Bridgeman techniques to observe the creep of rocks and he had an experiment set up in the basement here of Jefferson on that subject. What they do you see is B and I served on this as a senior fellow about six different years in the postwar era, but they had me come down to Eliott House and they had something like the six Senior Fellows had lunch and then they invited me in to be questioned about what I was interested in and what I was doing, etc.
So that group included Whitehead, Arthur Nock, Paul Buck was then provost at the university, and a wonderful man named Fred Hisaw, who was a biologist. We used to call him Mr. Sex or something like that because he was an expert in many respects. He was a Senior Fellow. Anyway —. Well, I think I talked a little bit about the interest in these timescale issues with Whitehead. Because of course Whitehead had his own relativistic theory at one stage. But then they also asked me about what I read, and I told him my wife had put me onto reading Dostoevsky recently and what did I think.
Oh, I thought it was wonderful but also very tearing you know. I think it was Crime and Punishment or whatever. Oh boy, that was quite a group, because one of the first ones I met was a man named John Kelleher, who was a Celtic historian and scholar — not a linguist particularly, but he was an Irish American, and I soon discovered, the first day I met him — He ended up being the professor whose professorship was endowed by Henry Shattock. But in any case, he, when he learned I came from Ridgeway he said he knew about the Battle of Ridgeway.
And he said — turned out that his ancestors had helped organize the Irish into a raid which became called Penian raids, which was an attempt to take over Canada for the United States — or to drive the representatives of the kingdom out. And this occurred in my home village, and there is now a little museum to it and so forth. In Civil War, the Union Armies who had driven back some southern raiders who were raiding all along the Ohio River Valley and so forth, and he was considered an extremely able warrior.
And he organized two thousand Irish immigrants who had been in the Civil War as well to cross the river and attack Canada. And it was the Battle of Ridgeway and it lasted only one day, but John and I have had that relationship ever since. I just read his obituary because he died January 1, Not physicists, but there were — Don Griffin was a biologist and very — Oh yeah, and Don Griffin is the man who studied homing of bats — I'm sorry, the homing of pigeons — and he was the man who studied the sonar properties of bats.
And he had the help of a retired Harvard physicist called George Washington Pierce, who had studied insects as well and had ultrasonic equipment that he lent to Don Griffin. Don Griffin, he was still with us in a dinner party last week. And then there was a man that helped me, it was a chemist. The chemist junior fellow, Martin Ettlinger, got to use the chemistry professor's laboratories at Radcliffe over in the old Radcliffe Byerly Hall. Ettlinger helped me there was — he helped me make solutions of gallium chloride — that I could look for the NMR.
I measured a lot of nuclear magnetic moments using NMR. Another distinguished biologist was Carroll Williams who went on to discover a growth hormone by his studies of insect physiology. Well let's now look at the postwar world. Just a general question. When the war started physics was really interrupted. And there was building intensity in physics in this country in the late thirties.
And then everything stopped, and now suddenly the war is over. Was there a sense amongst you and your other friends that you were going to pick up where you left off, or how did you sort of think you were going to get started again? Well, I think, well as I say, in the dismantling of the Radiation Lab I saw all those people going back to where they'd come from mostly, and the dominant thing of physics in those days was of course nuclear physics and cyclotrons and all that.
And Harvard was rather limited in that respect because it had lost its cyclotron to Los Alamos. And Ken Bainbridge, who had built the cyclotron before the war, and it was quite successfully operational before the war, whereas MIT had attempted to build one that didn't work very well, so they used the Harvard cyclotron quite a bit.
And I profited from that a little bit in the postwar era because they were generous to us to use the postwar MIT cyclotron for radiations occasionally. And so, because they felt an obligation from our willingness. But anyway, no, I think people were certainly looking for using the new technologies, and of course people like — one of the most distinguished people at Radiation Lab was Jim Lawson for example, and he went off to General Electric in the new Knowles Lab I guess it was.
But he in particular oversaw the building of a betatron there. Now was it a betatron or a synchrotron? I think it was — I know that he sent some information at one time about the volume of stuff that the pumps had succeeded in pulling out of there. It was tons. It was amazing. But anyway. So if you've read Alvarez's book, people like Alvarez and Bill Hansen, they all tried to make accelerators and apply that aspect of the technology. But I, with a man that went to Yale after the war, Bob Beringer, used to go to that lunch there for quite a long time quite often.
For 40 cents you'd get this marvelous lunch. They made their own bread, they made their own Boston cream pie, and all these things. It was a bakery and it was a delicatessen. And so then as things started disintegrating B I don't know whether Beringer was still around, but he ended up at Yale building accelerators at Yale. He was down the hall and across and I used to spend a lot of time over in his office because in what I was doing in this thing, the Magic T and all, was very close, that was their concern.
And so, and another person in his group that I spent a lot of time with was Carol Montgomery who was the co-author with them on that book. He died soon after the war but — And he had been Bob Beringer's thesis advisor before the war. They did the first directional correlations, they did the directional correlations of annihilation radiation, positrons. Of course we walked from 77 Mass Ave. And he thought, they used to talk about that at Columbia.
And of course that was the after effect of [C. And but Henry couldn't remember quite why they didn't think it would work. No, they didn't say that. I wonder how that comes about? Henry said he would do a literature search and try to find what happened, what would be the case. And he came up with this paper of I.
And I. Waller had calculated for electrons, not nuclei, and Henry sat down and converted it to apply for protons as compared with electrons in solid and he came out with a view that it might be an hour or so. But he made some — And this was that he realized it was not the first order effect but the second order effect that dominated because that allowed you to integrate over the whole spectrum of phonons and that at room temperatures and well above the lattice temperature you could have that help, and so he gave out with the view that it might be some hours.
But it turned out that he used incompatible numbers in the long run. If he had done it right he would have been more discouraged in the hours because our system was designed to work even though it would be hours. Because once the relaxation had happened our big cavity and the rf level we would use with it would be so low that it wouldn't disturb the equilibrium significantly in less than several hours.
And that was one of the reasons we used this big cavity instead of a coil. But the other reason was that we were so immersed in microwave technology and so forth that we never thought of not, of just using coils and capacitors. Let me ask a little tricky question I think. You and Torrey and Ed Purcell, when you were walking to lunch you were all young and you were all early in your career.
What established Purcell as the head of that experiment? Well, he had made the suggestion. He raised the question of could you do it, and as you say, it was the fact that in his book writing he had been writing down the history of the discovery of the absorption due to water vapor, and he came to the realization that there were just two particular levels whose energy difference was just equal to that frequency. And although there was a system of hundreds of levels, and if anybody looked at it carefully enough they might have discovered that particular pair, but [David M.
So and of course there you didn't have a population problem. Well, it's the same differential population for those levels because of their energy difference, but it's populated at the atmospheric temperatures through a very large number of those levels. Although in a sense I think that all three of us were pretty important to it. Ed told me that when you were doing that experiment that you, Bob Pound, knew more about — and I think he said signal-to-noise — than anyone in the country.
Well, I think that's an exaggeration, because there were some people at Bell Labs, and there was a man who ended up for a while at British Columbia and then at Michigan, Michigan State, who wrote books on these subjects. But there was a man named Rice. I gave a course here when I was a junior fellow on limits of sensitivity and detection and so forth which actually was under, oh, engineering science and applied physics department, a predecessor of applied science to the division, and that was in ' Was it spring '48? But I learned an awful lot of that, and the real details of what I could talk about from my having the manuscript of Lawson and Uhlenbeck, which was one of the Radiation Lab's books, and that was really the best work of that kind that existed then.
Do you see your role in the Purcell experiment sort of analogous to Hansen's role in the Block experiment? Not that much, because I think that Hansen's role was greater than most people realize, in that he was the man that really understood how to make the thing work, the circuitry and everything. And I have seen his notebooks from May of , which was well before we even thought about it, in which he was designing a balanced amplifier for this thing.
Then he had a question under this that said something about how the nuclei would react to this or that. Pretty much, yeah, I guess so. Well, Ed and I participated in designing that cavity, and I had my technician build it. I had a very good private kind of — Charlie Rowe, who had been my sort of electronics and machinist private guy in my little subgroup there all through the last couple of years, and he hadn't anything much to do and was waiting for an opportunity for his new job after the war, so I put the drawings we had made and asked him to build it, which he did.
And he was very good. And actually my college mentor, Grant Hector, hired him after the war to National Union Radio Company which he had taken on as the head of something or other. Because you see he had spent the war years after I left, then he left and joined Merle Tuve in the proximity fuse development. So he became very involved in making these little hearing aid, well, these little vacuum tubes for proximity fuses. Let me say — I should have probably made it clearer.
Which of course has had enormous significance in the following years. Why don't you just tell us about the experiment? Oh, well, as I say, the experiment was based on using a balanced bridge. In one arm the cavity that contained the absorbing sample, which was paraffin wax. We had about 2 pounds of paraffin wax in this cavity, and that's some stuff that Purcell had bought at the little local grocery store on the way over that evening. And we melted that and poured it into the cavity. And on Thursday, the 13th of December, we spent the evening trying — We had everything set up.
I brought everything up from MIT. And, you know, that's right. All of three of us were full-time employees, and we were doing this clandestinely. And he heard that talk by Bohr, and he decided he wanted to see for himself, so after the talk he went back to the lab at Columbia, set something up and saw these big flashes of tracks on his — I don't know what kind of detector he was using, but they were big things that indicated he was seeing this big energy from the fission. And so then The New Yorker said he closed it down and thoughtfully went leaning into heavy weather.
It was pouring rain or something like that, and walking, contemplating about the new world that was opening up this way. So when we had that Thursday night there was a snowstorm here. And this was almost the first time I'd been here. No, we had come over in preparation for that experiment. We had to measure the field of the magnet and we got — Ed had the machine shop here make new pole pieces to try to get a uniform field and used Rose shims on those pole pieces which turned out to be overdone.
And but we brought down from the attic, from not the attic, the fourth floor electricity lab, a wall galvanometer called a ballistic galvanometer in order to measure the field with the flip coil technique. And I don't know if I ever showed you that. Did I ever show you that —? Let's just pause a minute. I'm going to switch the tape. We were talking about calibrating the magnetic field on the night of Thursday, December 13th. And we had the thing, the magnet, calibrated and the pole piece, that was after Ed had had the pole pieces modified by the machine shop here.
And the other item that Harvard's contribution was the general radio signal generator. It was applied as a 30 MHZ source. Other than that and the magnet the rest of it all was stolen from MIT. I use the term stolen as a euphemism I suppose, but one of the things that came from MIT was also, it came out of my crystal test set thing, was this Hallicrafter high-frequency radio receiver.
That performed the main amplification and detection whereas it was preceded by an MIT Radiation Lab preamplifier that was used from radar, because, see, 30 MHZ was the frequency of the intermediate frequency radar, and so we had the very lowest noise amplifiers available in those days. Henry Wallman designed that fancy circuit which got the noise figure down to 1 or 2 db, and that was at the front end.
So, and then it fed the Hallicrafters, which came from my apparatus in my lab at MIT and it had a meter at the output which was the only way of seeing the signal. You watched this meter and you would balance this bridge by adjusting the amplitude on one arm compared with the other, adjusting the frequency into the peak of the transmission through the cavity, and then balancing it down by adjusting the intensity and the phase.
And the phase was adjusted by using little line stretchers that were intended for centimeter wavelength and here we were working meter wavelength, so we had a line of these things so that you could get enough adjustability. And then by Thursday everything was together, and then we started trying to see if it would work. Yes, we started the experiment on Thursday evening, which meant turning on the magnet and getting the water flowing through, the water cooling on the big magnet.
And the control of the magnet was a rheostat on a panel on the wall, which was many feet away from where the experiment was, and the meter sat on that table, and everything in this balanced bridge was terribly microphonic so you didn't want to touch the table or anything when it was balanced down. Because you could only balance it down so far, because the frequency sensitivity of the two arms of that dumb bridge were different, because one had the cavity and the other just had an untuned attenuated path. So you could only balance it down to about, by 60 db or so, because the noise sidebands weren't balanced in the same way on both sides.
So that would determine how much rf level we could use. And then we adjusted it down until we could no longer balance more and the meter was standing at, reading noise, so then we started adjusting that rheostat around the field which this calibration said would be the right value, because we knew the g value from Rabi. And we worked from mid-evening until three or four in the morning trying, rebalancing and adjusting and so forth.
No result whatsoever. So finally I had to go off in that snowstorm without the contemplation that I could think about what was happening in the future. I was the only one that had driven, and I drove Ed back to his house and Henry back to where the Torreys were renting and living down near Mt. They spent the evening together wondering what we were finding, and I had to say we hadn't found anything. But we made a compact about coming in on Saturday, thinking maybe it was the relaxation time, it was too long. Although having spent all that time, it was relaxing all that time, when you think about it.
Because the field was on also at the time. So anyway, Ed agreed to come in around seven in the morning on Saturday and turn the magnet on and let it cook until we would come in. Because in those days we still were expected to work on Saturdays in principle, although I don't think anybody would fine us if we hadn't. But we came in about two in that afternoon and then we started all over again. And the same effect. Everything happened. Nothing happened. The meter never made the bumps. It was amperes at volts, so that was a lot of power.
We turned it all the way up to the top and then came down slowly. And as we came down through 80 amperes it went bump. There it was. And that's because in this calibration we were seeking it at something like 73 amperes. Well, we did. We went plus and minus 10 percent relative to that thinking we couldn't be wrong by more than that.
And the fact was we were wrong by more than that — not because our calibration was wrong, it was fine, but it was what we had forgotten and didn't look at it properly was that the magnet was saturated. So it took all that more amperes to get 2 more percent field. We were only off 2 percent in the calibration, which is pretty good for that kind of system, but it took 15 percent more current in order to get that 2 percent more field. That's right, that's right.
And one of these pieces of paper has Henry's signature on it — not Henry's signa — Oh, there is a copy of the circuitry, but — Yeah, well —. Oh, yeah, we were very — we first saw that we had now something to go with to what we could see what we were going to be doing for a while. And I would give up my ideas of building another atomic clock for a while — although I was supposed to be. At Harvard there was a — you know E. Chaffe was. He was the main electronics specialist at Harvard who built big vacuum tubes and things. But he ran the electronic research lab, and he had some graduate students.