stein is synonymous with the scien­ atomic bomb project — an involve­ 17 March with a very broad pro­ tist in the popular imagination. Each ment which troubled Einstein for the gramme covering sciences, humani­ budding genius is foisted with his rest of his life. Another indication of ties, human relations and theology. name. His distinctive features are the esteem in which he was held There is a long list of sponsoring the popular vision of the face of the was the offer in 1952 to become institutions including CERN. Leon scientist. Many of the concepts from President of the State of Israel. Van Hove, CERN Research Director his relativity theory have now Albert Einstein was a man of great General, is Chairman of the Inter­ seeped into popular culture. stature both as a scientist and as a national Committee and many He had the respect of people from human being. He developed a close other high energy physicists will be all walks of life. He was blessed with relationship with the English phi­ giving papers or chairing session a great love of music and had consid­ losopher Bertrand Russell and a very (C.N. Yang, A. Salam, W. Thirring, erable ability as a musician. He had a Russell-like statement, from the V.Weisskopf, E.L Feinberg, A. Zichi- deep sense of social responsibility 1973 book of Einstein's 'Ideas and chi...). and took a firm stand on many of the Opinions', makes a fitting conclusion At the Institute for Advanced important issues which welled up to this short tribute — The ideals Study, Princeton, where Einstein during his life. which have lighted my way... have worked from 1933, an 'Einstein His eminence in science, at a time been kindness, beauty and truth.' Centennial Celebration' will be held when science and technology were Many events are being organized from 4-9 March. The emphasis is on leading to so many changes in every­ throughout the world to mark the specific aspects of Einstein's scien­ day life, inevitably led to his being anniversary of Einstein's birth. tific work and many leading figures called into the political arena. This The main event is being held in in high energy physics will be had its most telling moment in 1 939 Bern, Switzerland, where . Einstein involved (C.N. Yang, W. Panofsky, A. when, prompted by Leo Szilard, he was based when he did his work on Pais, E. Amaldi, T. Regge, S.Wein­ wrote the letter to President relativity. An 'Albert Einstein Cen­ berg, P. Dirac, R. Feynman, V. Weiss- Roosevelt which initiated the tenary' will be held from 13- kopf, Y. Ne'eman, G. 't Hooft...). Some developments in detection techniques and applications It is a rather obvious statement that chine can reveal will be observable where. This article pulls together developments in particle detection by available detectors. some recent developments in detec­ techniques have been crucial to Since the advent of high energy tion techniques and some indica­ developments in particle physics. It accelerators, the abilities of particle tions of applications in other fields. is not only the advancing abilities of detection have been revolutionized. accelerators in providing higher en­ The precision with which it is now Multistep avalanche chambers ergies, intensities and qualities of possible to time the passage of a particle beams that have taken our particle, to locate it in space and to Perhaps the most significant of all understanding of the nature of identify it, and the rate at which this the advances in detection techni­ matter further but also the abilities of information can be collected, are ques was the invention in 1968 of detectors to untangle the particle orders of magnitude greater than multiwire proportional chambers interactions which are produced. It is they were twenty years ago. and drift chambers by the group led for this reason that every study of a As usual, such technological ad­ by Georges Charpak at CERN. These new machine carries with it a study vances, which were pushed in the detectors locate the ionization ini­ of detection systems to ensure that cause of high energy physics, have tiated by the passage of a charged the new interactions that the ma­ also found many applications else­ particle through a gas, either by 4 CERN Courier, March 1979 The different steps of the multistep chamber which may prove to be another significant advance in particie detection techniques. The role of the various steps is described in the article. drawing signals from wires closest to the particle (MWPCs) or by meas­ uring the time taken for the electrons liberated in the gas by the particle to reach a wire (drift chambers). These detectors, now in universal use in high energy physics Laborato­ ries, brought high spatial resolution (1 mm for MWPCs, 100 |im for OCs),good time resolution (25 nsfor WIWPCs, 500 ns for DCs), multipar- ticle detection capability, high rate (able to record several million tracks per second), continuous sensitivity to the passage of particles and the ability to draw both spatial co-ordi­ nates from one detector (which has proved of great use in monitoring neutral radiation). Their applications have extended into other sciences (nuclear physics, solid state physics, astrophysics) and the applied sciences of medicine and biology. There has been a constant effort to improve the abilities of these detectors in many Laboratories and articles and news reports on these study of the basic physics of energy are collected. The tricks are applied developments punctuate CERN deposition in gases and the subse­ in a 'multistep' chamber in the COURIER pages for the past ten quent behaviour of the ionization following fashion. ears. products. This study has yielded Step 1 is a preamplifier, with elec­ Now there is particular interest in several surprises and the latest one, trode planes A and B, in which the increasing the rate at which MWPCs again unearthed by the Charpak ionization caused by the passage of can record particles and in improving group, could result in another signif­ a charged particle is multiplied by their accuracy in locating the particle icant step forward. some factor which can be limited to in space. For example, (i) one poten­ A major limitation on the possible about 103. Some of the electrons tial application in medicine, where rate appears to be the result of the (perhaps 20%) arriving at the plane high energy proton scattering could length of time needed for the space of anode wires, B, have been be used to do three dimensional charge of the positive ions, produced observed to penetrate into the drift scans of the body, would benefit in the region of the signal wires space between the planes B and C. from the highest possible rate so as where the electron avalanches are In Step 2 the drift time for the elec­ to keep exposure times down, (ii) concentrated, to die away. trons to travel between B and C can biological studies using X rays gain They decided to investigate ways be set so as to give faster detectors from speed and accuracy so as to of reducing this effect. The first (scintillators and logic elements) study living, moving systems, (iii) the trick is to allow only a selected frac­ enough time to decide whether to new meson factories flood experi­ tion (corresponding to interesting record the particle. ments with intense particle beams events) of the ionization, initiated When the decision is positive, and are crying out for detectors to in a chamber by the passage of electrode C is pulsed so as to keep pace with the beam intensi­ many particles, to develop as a full allow the electrons through into the ties... avalanche. The second trick is to signal collection chamber between A lot of the steady advance in the reduce the 'multiplication' in the planes C and D. Here, Step 3, there abilities of MWPCs has followed the actual chamber where the signals is another stage of multiplication of CERN Courier, March 1979 5 about 103 so that the total multi­ to communicate the signal further. The streamer chamber has not, plication from Steps 1 and 3 is In the tests at CERN, positional however, taken over as a universal above 105 which is the customary accuracies of 150 |im along the detection technique. Rather it con­ figure acceptable to standard anode wires and 250 jim in the tinues to be applied in particular MWPC electronics. However, the direction perpendicular to the wires experiments where its properties are creation of ions in the signal collec­ (better than the wire spacing given adapted to the particular detection tion chamber is reduced by a factor the possibility of interpolating the needs. One such application has of 1 03. In addition, only signals from charge because of the avalanche aroused a lot of interest over the past wanted particles have been allowed spread) have been achieved. The year. It is the^development of a high through which again reduces the ion rate capability of such multistep resolution streamer chamber by the creation. avalanche chambers is at least two group of Jack Sandweiss at Yale These two manoeuvres, by greatly orders of magnitude better than that They have installed their chamber at reducing the ion space charge of conventional MWPCs. A great Fermilab for a (comparatively) high problem, greatly improve the effi­ deal of further work needs to be done statistics search for charm parti­ cient detection of selected events, before practical detectors can be cles. amidst a flood of other radiation, built but the results so far are very The need for high resolution such as is often required in high encouraging.