Hermathena publications by JJ

In November 1953 there was a special issue of Hermathena to commemorate the Berkeley bicentenary, which was celebrated at an international conference held in Trinity College in July 1953. There were 70 universities present from all over the world. Eamonn de Valera, then Taoiseach (Prime Minister) opened an exhibition of Berkeleiana in the College Library. The delegates were received by the President Sean T O'Kelly. The keynote lecture was given that evening by JJ on Berkeley's influence as an economist, with professor G A Duncan in the chair, the vote of thanks being proposed by Senator Professor George O'Brien of UCD.

This paper can be regarded as a review of all JJ's work on Berkeley to date, and is therefore a candidate for reproduction in full. It can perhaps be regarded as the pinnacle of JJ's academic career. I regret not having witnessed it, having been in France at the time. In fact, I was not even aware of it; I was taking part in a summer school on theoretical physics at Les Houches, near Chamonix, in the company of people like Bryce de Witt, Rudolph Peierls and Bill Shockley (of transistor fame), and there was a postal strike, so that I had no word from home. I noted this coincidence, for the first time, at the time of writing in November 1999, and I savour it as the measure of the width of the gap which was between my father and myself in the early 50s.

For the moment I quote JJ's penultimate paragraph: 'John Mitchel, Thomas Davis, Isaac Butt, and in our own day Arthur Griffith, George Russell and Eamonn de Valera, have frankly recognised the debt the nation owes to the heart as well as the head of this great Irishman.'

Scientific Publications by RJ

The Pic du Midi Observatory, as it was in 1953. The photo was taken from the top of the mountain; the Ecole Polytechnique laboratory was slightly to the left of centre. You can display a larger version. There are also some additional pictures accessible.

All the 'heavies' were there: Barker, Butler, Astbury, Newth, Page and Armenteros (the Blackett group) from Manchester, RW Thompson from Indiana, Bridge and Rossi from MIT, Powell, Menon, Perkins, O Ceallaigh, Friedlander and Fowler from Bristol, Bhaba, Peters and Biswas from Bombay, the Rome, Genova and Milan people led by Amaldi and Occialini. The sessions were presided over by the star pioneers of the field: Blackett from Manchester, Leighton from Pasadena, Peters from Bombay, Reynolds from Princeton, Leprince-Ringuet from the Ecole Polytechnique in Paris, Amaldi from Rome, Bhaba from Bombay, Powell from Bristol, Rossi from MIT.

The conference explored competitively the utilities of the cloud-chamber and ionographic emulsion as tools; the bubble-chamber was a competitive threat on the horizon, as indeed was the next generation of particle accelerators. Cosmic rays were still the main source of particles having energy fit to produce heavy mesons and hyperons from protons and neutrons. We did what we could with the tools to hand. When the new tools arrived in the mid to late 50s, the community split into those looking at cosmic rays, seeking their origins, energy spectra etc, and those interested primarily in high-energy nuclear physics; the latter gravitated towards the accelerators as sources, continually refining their experimental technologies.

The Ecole Polytechnique physics laboratory had a three cloud chamber groups and an emulsion group; the one of which I was a member ran a cloud-chamber installation at the Pic du Midi which consisted of two large chambers, the upper one being in a 250KW solenoid, producing a magnetic field for measuring particle momentum, and the lower one containing lead plates, for measuring the range of stopping particles. Other members of the group were Bill Fretter, who had joined us from the US on sabbatical, Bernard Gregory (who subsequently headed the CNRS the main French science funding agency), Andre Lagarrigue, H Mayer from Sao Paolo in Brazil, F Muller and Charles Peyrou. Gregory was the group leader; he and Peyrou had US experience.

The double cloud-chamber, solenoid and control system in the Pic du Midi laboratory, as it was in 1953. You can get an expanded version. I give also some photos of the supportive automation equipment, and other Pic du Midi installations, including the telescope used by the astronomers.

The installation was basically an automated production system on an industrial scale. The solenoid was a heavy-gauge copper tube, through which the cooling water was pumped, in a closed-circuit system, with fan-cooled radiators on the roof. When starting up in the winter, one of the chores was removing the ice from the fans, the outside temperature being -20C; this had to be done because otherwise the fans would vibrate dangerously. There was a safety system which cut the power if the circulation failed. The cloud-chambers were temperamental beasts; getting them to work cleanly was somewhat of a black art; Gregory and Peyrou were the experts. There was an automated system driven by cams and timers which ran a series of slow expansions, the purpose of which was to bring down any stray condensation nuclei in clouds of droplets which were allowed to settle. The clean chamber then awaited its moment of glory, when the surrounding electronics detected a charged particle coming in the top, and nothing coming out the bottom; this way it was hoped to find particles coming in with a measurable momentum which stopped in the lead plates of the lower chamber.

When such a combination occurred, fast expansions were triggered, by a 2-stage pneumatic process; large vents behind the pistons were rapidly opened by deflation of 'boudins' which sealed them; the pistons crashed back against stops, the alcohol-argon mix in the chambers became supercooled, and drops condensed on the ions left by the passing charged particles. After a calculated delay, to allow the drops to grow, the chambers were illuminated from the side by flash-tubes, the chambers with their tracks were photographed, and the stereo cameras were wound on.

I found myself contributing to the maintenance and development of the electronics. I had picked up in my final year in TCD some experience of pulse electronics thanks to a course laid on in the Dublin Institute of Advanced Studies by McCusker, who had a cloud-chamber experiment running in Merrion Square. The key text was Elmore and Sands, which enshrined the pulse electronics experience from the Los Alamos 'Mamhattan Project' (ie the atom-bomb). Surprisingly this had not reached France yet, and I found myself regarded as an expert. The electronics had been developed at the then existing level of technician-ship, with the gain of amplifiers dependent on various random and time-dependent factors. I introduced the principle of the negative-feedback amplifier, where the gain depended on the ratio of two resistors, and was more or less independent of the state of the vacuum tube. (Transistors were then unheard of.) Getting a good square pulse, with fast rise-time, for use in coincidence and anti-coincidence logic circuits, was embedded in the Elmore and Sands text, and we absorbed it avidly.

There was also a problem with the flash tubes, which were driven at high voltage from a bank of heavy-duty capacitors ('ici, c'est la chaise electrique'). Sometimes one of the 3 flash tubes did not work, and in this case the chamber illumination would be uneven, and the picture useless. I rigged up a handy little indicator, with neon lights, which showed whether all 3 flashes had worked, and if not, which one was at fault. This was regarded as pure magic, and from then on my reputation was assured.

The yield of good photos was not great; we did a rough scan at the Pic, picking out the probable good ones, which were sent to Paris for analysis. The curvature in the magnetic field, giving the momentum, was measured with templates. The estimation of velocity was rough and ready, depending on the droplet density of the track. We identified significant numbers of 'V-particles' and 'S-particles', as they were known at the time; the system gave us the means of measuring the mass of 'S-particles' because we had the momentum in the upper chamber and the range in the lead plates in the lower chamber. We were able to report a mass of about 920 electron masses at the Bagneres conference (cf p113 of the proceedings), which was non inconsistent with the 'S-particle' being the same as the 'K-meson' as had been identified by Cormac O Ceallaigh when working with Powell in Bristol.

In another paper on p101 of the Proceedings there is a description of the experimental rig, and some analysis of particles decaying in flight in the upper chamber, including one possible 'superproton' (hyperon). A third paper on p26 attempts to interpret a nuclear interaction in one of the lead plates, caused by a negative particle of momentum 1080MeV/c, from which emerges a 'V-particle' and some gamma-rays indicating an uncharged pi-meson.

While none of these events were 'world-shaking' in scientific terms, the experience was part of a global scientific culture which has thrived and continued to give us increasing insight into the laws of nature. It was my privilege to have been part of this culture, and to have benefited from it in human terms. One of the lasting memories is of the relationship between the members of physics community and the technicians who worked with them making their equipment, and getting it to work; this was based on mutual respect between people having complementary skills, unsullied by exploitation. I share with JD Bernal the vision that this might be a glimpse of the human side of the productive process in some post-capitalist future, owned by those directly concerned and not by some remote alien capitalist consortium.

I should perhaps record an exception; Mayer, who came from Brazil, from an upper-crust Hispanic background, refused to help with the cleaning of the windows of the cloud-chamber, insisting that this was not physicists work. It is actually quite a crucial part of the preparation of the chamber when stripped down for maintenance, and everyone concerned had to know how to do it correctly; it is part of the 'black art'. This perhaps says something about Latin-American society. In fact, most of the physics world, being usually at the frontiers of knowledge, has to live with the need for hands-on mastery of its technical practice by its scientists, who then, when they can, pass the knowledge on to the technician community by apprenticeship or osmosis. There is no room for disdain of dirty-handed processes.

The Bagneres conference reported the above work under the following titles:

Production of a V01 by a 1BeV negative primary, RJ with WB Fretter, BP Gregory, A Lagarrigue, H Mayer, F Muller and C Peyrou; p26.

Quelques Resultats sur les V-chargés; with group as above; P101.

Mesures de Masse de Particules S par Moment-Parcours, with group as above; p113.

These were my first serious publications; a revised and updated version subsequently appeared as a Physical Review Letter. They described several particle-decay events, indicating a mass of around 900 electron masses, consistent with what was subsequently called the K-meson, as well as one possible more massive 'superproton' (subsequently labelled 'hyperon'). The mass measurement, 922 +/- 41 electron masses, was low, and I often wondered was this due to the fact that I had, for one of my earlier contributions to the project, calculated wrongly the stopping power of the lead plates in the lower cloud-chamber. This experimental technology was however shortly to be rendered obsolete by the arrival of the liquid-hydrogen bubble-chamber.

Return to Dublin

Cormac O Ceallaigh attended the Bagneres conference, and we met there for the first time. He had been earlier in University College Cork, where he had collaborated at a distance with CF Powell and the Bristol group who had pioneered the study of mesons using photographic emulsion. He then took leave of absence from Cork and worked for a time in Bristol, improving on the methods of measurement of ionisation and momentum of charged particles, based on the properties of special (Ilford G5) photographic emulsion, adapted for ionographic measurements. During this period he discovered the K-meson, which had mass intermediate between the pi-meson and the proton, and which appeared to decay in several distinct modes. He was thus a recognised pioneering luminary of elementary-particle physics, and in that capacity had just then secured appointment to the Chair in the School of Cosmic Physics in the Dublin Institute of Advanced Studies. He regarded encountering the present writer at Bagneres as a piece of luck, and he recruited me on the spot to join his team.

This photo was taken at a reception in connection with the Bagneres confeence; Mairin and I are talking with Ferrand (?) who was related to, and worked with, Leprince-Ringuet in the Paris laboratory. Could it have been Neil Porter, later in UCD, on the right? I am open to suggestions who the other might be.

During our spell in Paris my then wife Mairin, whom I had married in January 1952, had joined the team at the Ecole Polytechnique and trained as a 'scanner'; she learned how to scan with a microscope through the volume of the ionographic emulsion, recognising 'interesting events' and recording their exact position, to within a few microns, enabling them to be studied in more depth using various analytical techniques. She had become very good at this, and O Ceallaigh recruited her also to the team.

Back in Dublin from September 1953 we started examining some G5 emulsion which had been exposed at high altitude to cosmic rays, using a balloon, flown and recovered at sea, off Sardinia, by courtesy of the Italian navy. This had been set up by Guiseppi Occialini, of Milan University, who had worked with Powell on the pi-meson; the subsequent collaboration which developed involved various additions to this Bristol-Milan axis.

Mairin and I, during our first few months of work on the Sardinia material, 'got lucky'; she picked up the track of a relatively heavy particle which emerged out of a 'star' (ie where a high-energy particle had encountered a nucleus and shattered it into many visible components) and which came to rest in the emulsion, causing another small 'star'. One can tell a particle is coming to rest by the way its 'scattering' (ie tortuosity of its path) and 'ionisation' (blackness of its track) increases. She recognised this as unusual and drew our attention to it; we immediately knew we were on to something, and began intensive work to characterise it. The mass was some 2300 electron masses, and the amount of energy involved in the small terminal 'star' was such that it implied that much of the decay energy had gone into a neutral particle, probably a pi-zero, which would be invisible. The fact that it had ended up disrupting a nucleus implied it was negatively charged. There were at this time only two other such events in the world, both subject to uncertainties. This one was the clincher; it was later labelled the Sigma-minus, and entered the extended family of 'hyperons', which can be visualised as nucleons with a meson stuck on. This earned us our first DIAS paper:

Evidence for the Nuclear Interaction of a Charged Hyperon Arrested in Photographic Emulsion; RHW Johnston and C O Ceallaigh; Phil Mag, ser 7, vol 45, p424, April 1954.

Shortly afterwards we got another one, enabling us to produce another paper; by this time, between Dublin, Bristol and Padua there were 5 such 'events' in the world:

Further Evidence (etc as above); Il Nuovo Cimento; 1 Marzo 1955, 1, 468-472.

This Italian journal of physics, as well as having deep historic roots, had become an important vehicle for high-energy particle physics, under the influence of Amaldi, Rossi, Occialini, Fermi and others, resisting for a time the concentration of all such results into the US-based Physical Review. It published mostly in Italian but accepted papers in English. For a time I did abstracts from it for one of the abstracting journals, picking up enough Italian to do so by a process of adapting school Latin.

We continued to analyse the Sardinian plates; the thick G5 emulsion layers were mounted on glass plates for processing; their positions relative to each other in the original block from which they were peeled off were determinable thanks to X-ray markings at the edges, so that it was possible to 'follow through' long tracks from one plate to the next. We picked up several negative K-mesons, which came to rest causing nuclear disintegrations. Between ourselves in DIAS, the UCD group and the Bristol group we were able to publish a another pioneering paper:

Observations on Negative K-mesons; MW Friedlander, D Keefe and MGK Menon (Bristol), RHW Johnston and C O Ceallaigh (DIAS), and A Kernan (UCD); Phil Mag ser 7, vol 45 p144, February 1955.

Denis Keefe, then at Bristol, was with the UCD group, led by TE Nevin; he was then spending some time at Bristol, which was the world centre for this experimental technology. Menon had worked previously with O Ceallaigh when the latter was in Bristol; shortly afterwards he returned to India where he became a leading physicist and adviser to the Government on science policy. Anne Kernan emigrated to the US and ended up with the chair of physics, I think in Michigan. Keefe also emigrated to the US; I think to Berkeley California; he participated in an international conference in Physics in Industry which took place in Dublin during the 1970s, during which I encountered him. (I gave advance notice of this in January 1976, and then reported on it in April of that year, somewhat disappointed; the conference had taken place in March.) Other members of the UCD group were Frank Anderson and Alex Montwill. Unfortunately O Ceallaigh and Nevin fell out, so that the emerging Dublin group, between the two locations, did not develop coherence, as it looked like it might do at the time this 1955 paper was published.

We continued to analyse the Sardinian plates, and came up with another unusual event, a K-meson which decayed directly into an electron. We were able to establish this using innovative measurement procedures developed by O Ceallaigh, measuring the change of ionisation along the track of a stopping particle, as well as multiple Coulomb scattering, with precision follow-through of the path of the decay electron in successive plates. We were establishing the utility of an innovative experimental technology, of which we hoped to make extensive use subsequently. This work was published, at a pioneering time when single events were sufficient to justify a paper:

Further Evidence for the Electron-Decay of K-Mesons; RHW Johnston and C O Ceallaigh, Phil Mag ser 7, vol 46, p393, April 1955.

The success of the Sardinian experiment led the Powell group to organise a scaled-up project, the 'G-Stack', the largest ever block of ionographic emulsion, which would be flown with a balloon at a great height for a long time, in the hope of trapping large numbers of mesons and hyperons generated by nuclear reactions with high-energy cosmic rays. By assembling a large team of co-workers, using standardised techniques, it was hoped to find out something about the decay processes of the positive particles, and the nuclear interactive properties of the negative ones.

This was an example of the 'sailing-ship effect': the last fling of an obsolescent technology, under the threat of replacement by an innovative successor. The high energy particle accelerator was on the horizon, with the liquid hydrogen bubble-chamber as particle detector. The writing was on the wall for ionographic emulsion in this context, and most of us knew it. Our last fling however was on the whole creditable.

The G-stack collaboration, in its first publication:

On the Masses and Modes of Decay of Heavy Mesons Produced by Cosmic Radiation; JH Davies et al, Il Nuovo Cimento, serie X, Vol 2, pp1063-1103, Novembre 1955;

had all of 36 named authors, 10 from Bristol, 6 from Copenhagen, 3 from DIAS (including the present writer), 3 from UCD, 9 from 4 locations, three in Italy and one in Brussels, and 5 from 2 other Italian locations.

This was perhaps a precursor of some of the massive collaborations which have developed in the European Union research community. It is interesting however how it was possible a group of 9 people, located in Brussels, 2 Milano locations, and Genova to work as an integrated team, led by Occialini, while the 2 Dublin groups, separated by 5 minutes walk, led by O Ceallaigh and Nevin, insisted on their separate identities. It says something about Irish academic politics.

The main result of this work was to establish the existence of 2 modes of decay where the secondary particle had a single well-defined energy, one being a mu-meson of 155 MeV, the other being a pi-meson of 109 MeV. It was also established that a small percentage of the mesons decayed to an electron and 2 other bodies, probably neutrinos, with a continuous spectrum up to about 160MeV. The details of these many-body decay spectra were subsequently elucidated using the artificial beams of mesons which soon came on stream from the big accelerators. Sail was overtaken in the end by steam.

This PhD photo, taken in the TCD front square, includes Mairin my wife, my mother Claire and my father Joe.

The present writer profited by the foregoing to the extent that it enabled him to carve a PhD thesis out of refinements in the experimental technology. Protons and pi-mesons coming to rest in ionographic emulsion are useful calibration signals, their masses being known exactly. The mass of an unknown particle can be estimated by multiple scattering measurements, provided the particle comes to rest. One uses 'cells' of varying length, such as to give 'constant sagitta' (ie as the particle slows down, and its path becomes more tortuous, you reduce the cell size to keep the average 'sagitta' a constant). The scattering is due to the electrical forces exerted on the particle by the clouds of electrons surrounding the atoms of the emulsion. It obeys a statistical distribution known as the 'Moliere', which has a 'long tail'. The latter is due to the fact that occasionally the stopping particle passes near to the nucleus of an atom, and suffers a wide-angle 'Rutherford' scattering, so called because it was by this means that Rutherford had earlier established that an atom had a nucleus. These occasional wide-angle 'direct hits' however were destructive of the accuracy of 'multiple coulomb scattering' for measuring masses of stopping particles. We got rid of them by using a 'cut-off' procedure; if a scatter was, say, 4 times the mean value, we declared it to be 'Rutherford' and kicked it out from the statistics. This however introduced an error, and the object of my work was to establish what this was, and enable people to correct for it.

This was boring but essential work, and the G-stack team depended on it. It also was useful in later life, when dealing with 'dirty statistics' emerging from techno-economic models, in business investment decisions. I regard this as an important argument for the utility of so-called 'pure science', additional to the intrinsic interest of the results. The paper was published:

A Scattering Calibration Experiment; RHW Johnston, n2 del Supplemento al Vol 4 Serie X del Nuovo Cimento, pp456-459, 1956.

I also profited by the G-stack work, in that we were able to use the mono-energetic pi and mu meson decay products of our K-mesons to produce a very exact ionisation-velocity curve on the low-energy side of minimum ionisation, up to about three times the minimum level. This was extremely useful, and rapidly became a standard curve used in all laboratories where ionisation was the measure of particle velocity. We measured ionisation using O Ceallaigh's 'mean gap length between developed grains' procedure, which he had earlier established as being statistically the most reliable. Jerry Daly in the DIAS workshop had developed a micrometer eyepiece, with spiders webs, which enabled the mean gap length to be measured rapidly and accurately. This also became standard equipment, and we exported it to some of the other labs in the G-stack group. This work we published, and I regard this as being my best from this period:

On the Relation between Blob-density and Velocity of a Singly Charged Particle in G-5 Emulsion; G Alexander and RHW Johnston, Il Nuovo Cimento, Serie X, Vol 5, pp363-379, Febbraio 1957.

Gideon Alexander was an Israeli student who joined us for a time; he subsequently may perhaps have become influential in the nuclear physics establishment in Israel, perhaps with nuclear weapons, I hope not, if so, it would be on my conscience that I had helped him establish himself in that mode!

Jack Lynch, later to be Taoiseach, was at that time Minister for Education. O Ceallaigh had to spend a lot of his time defending the very existence of the DIAS, and on one occasion the Minister Lynch visited the place. He encountered Gideon and the present writer working on the foregoing, and we explained to him as best we could what was going on. It became clear from his contribution to the conversation that he regarded Gideon as a 'foreign expert' we had brought in, this then being the dominant Establishment attitude to science. It never occurred to them that the DIAS was a place to which foreigners came to learn, from people like O Ceallaigh, Pollak, Synge and Lanczos who were, in their own scientific fields, world figures.

After the Berkeley 6 GeV accelerator became operative, there was a brief flowering the the ionographic emulsion culture, from which we benefited. A focused beam of positive K-mesons was set up, and we exposed a large stack of emulsion to it, using the status of the G-stack group as leverage. Thus, using O Ceallaigh's personal network, we were in a position to make use of the most advanced US-based technical resources, at marginal cost.

We analysed 3300 K+ decays, using careful statistical tricks to eliminate bias (O Ceallaigh was an expert at this), and using the techniques of mean gap length and Coulomb scattering which we had earlier developed to a fine art. From the analysis of 3300 K-meson decays we were able to determine a good estimate of the relative abundances of the decay modes; the decay mode giving an electron of variable energy up to about 250 MeV amounted to about 5%; we had pioneered the identification of this process with a single example in 1954. For our work on the energy spectra of the 3-body decay modes the Alexander and Johnston paper above was the key tool. This however was the swan-song of the use of emulsion in this context; the bubble chamber, in a magnetic field, later took over, with much higher precision.

We noticed in passing that the pi-mesons secondary to K-decay appeared to be about three times as interactive as the norm, and we chased this hare for a while, but as more statistics came in, the signal evaporated. We did however mention it cautiously in the published paper:

The Relative Frequencies of the Decay Modes of Positive K-Mesons and the Decay Spectra of Modes K-mu-3 and K-beta; G Alexander, RHW Johnston and C O Ceallaigh, Il Nuove Cimento, Serie X, Vol 6, pp 478-5000, Settembre 1957.

The work of the 'scanning' team was of course crucial to this analysis; they were acknowledged in the paper: Mairin Johnston, Joan Keefe, Moira O'Brien, Phyl Leahy and Peggy O'Hea. We had something here of the positive atmosphere identified by JD Bernal as typifying true science: a sense of camaraderie and team-work between scientists and technicians, with mutual respect for each others' disparate skills.

By this time we had passed the peak of the utility of ionographic emulsion technology; from now on it was a rearguard action to stay in the game at all. O Ceallaigh began to turn his attention to issues like the mass-spectrum of the cosmic ray heavy primaries, while I attempted to make something of the high-energy side of the minimum of the ionisation curve, without much success. As a by-product of the earlier work we re-looked at the K+ decays:

A Search of the Existence of Asymmetries in Positive K-Meson Decay; A Wataghin, G Alexander and RHW Johnston, Il Nuovo Cimento, Serie X, Vol 7, pp128-131, Genniao 1958;

but this was a wild goose chase; the effect might have existed had the beam been polarised, and the K-meson had spin 1. Presumably it gave some thesis fodder for Wataghin, who had come from Sao Paulo in Brazil and was working with Powell in Bristol.

The G-stack collaboration, with variable composition, produced 3 more papers on negative K-mesons:

The Interaction and Decay of K- mesons in Photographic Emulsion;

Part 1, General Characteristics of K- Interactions: B Bhowmik et al, Il Nuovo Cimento, Serie X, Vol 13, pp690-729, Agosto 1959;

Part 2, The Emission of Hyperons from K- interactions at rest: B Bhowmik et al, Il Nuovo Cimento, Serie X, Vol 14, pp315-364, Ottobre 1959;

Part 3 has no additional sub-title, but is in effect an addendum to part 2: D Evans et al, Il Nuovo Cimento, Serie X, Vol 15, pp873-898, Marzo 1960;

We participated in this work, though without great enthusiasm. It is of interest to note the composition of the authoring groups:

Part 1: Bristol had 7, DJ Prowse leading; there was one M René in Brussels; DIAS had the same triplet as above; UCD had Denis Keefe on his own; a group of 6 in University College London led by EHS Burhop had joined; there were 5 from Occialini's Milano group, and another 5 from Padova.

Part 2 had the same team, while Part 3 was somewhat attenuated: the Bristol group under Prowse was reduced to 4, the London group was reduced to 4, Burhop having left; the Milano and Padova groups were reduced to 2 each.

There were tantalising hints of phenomena such as parity violation which were subsequently established using the big accelerators; the main contribution was to establish that the K- when it came to rest and interacted with a nucleus routinely generated a sigma hyperon, and it proved possible to estimate the lifetime of the latter. This work was however rapidly superseded by the accumulating bubble-chamber material at the major accelerators, CERN and Berkeley. On the whole I jumped ship at the right time.

There was a paper produced for the second UN Geneva Conference in the 'Atoms for Peace' series, which took place in 1959. It was a re-working of the combined DIAS and UCD work:

Investigation of the Strong and Weak Interactions of Positive Heavy Mesons; G Alexander, F Anderson, RHW Johnston, D Keefe, A Kernan, J Losty, A Montwill, C O Ceallaigh and M O'Connell; Pergamon Press, 1959.

This I suspect was a political nod in the direction of the United Nations, Ireland having recently joined. O Ceallaigh probably delivered the paper; I don't think any of the others got to go. It could also have been a device by O Ceallaigh to try to draw to the attention of the Government that there was world-class scientific work going on in Ireland, on a shoestring. He had recently reported to the Government on the question of what to do about the offer by the US of a 'research reactor', as part of the promotional process for nuclear energy. O Ceallaigh pointed out in his Report that the cost of this 'gift' to the Government would be more than the total current funding for science in Ireland, and it therefore should be rejected, until such time as they set up a science budget fit to accommodate it. This episode I suspect must have influenced the Government to commission the subsequent 1964 OECD Report 'Science and Irish Economic Development', by Patrick Lynch and HMS 'Dusty' Miller, which in turn influenced the setting up of the National Science Council in 1970.

My last scientific paper is filed, in draft form, with some O Ceallaigh correspondence; he was in the end not happy to publish it because it was inconclusive. We had reached the fringe of applicability of the experimental technology, and were attempting to quantify the 'relativistic rise' on the high-energy side of the minimum. Prowse has supplied the raw material. We had in fact gone up a cul-de-sac, and O Ceallaigh recognised it:

On the Ionisation-Velocity Relation in Photographic Emulsion for Singly Charged Particles, 1961, unpublished, with MA Shaukat (DIAS) and D Prowse (UCLA).

A by-product of the foregoing was an opportunity to develop what amounted to an early on-line computer for analysing the multiple scattering results as they came out of the microscope, relieving us of a boring chore. I used dekatron tubes as decimal memory, borrowing a Harwell procedure. The programming steps were under the control of an electro-mechanical stepping switch, as used in telephone exchanges. Programming was by plug-board. It worked satisfactorily, and was fun to build. I published a paper on it subsequently; it is referenced also in the techno-economic series in the hypertext, and is available in abstract:

A Special-Purpose Computer for the Analysis of Measurements of Multiple Scattering in Photographic Emulsion, paper by RJ in Electronic Engineering, June 1963.

Some navigational notes:

Copyright Dr Roy Johnston 1999