A low background-rate detector for ions in the 5 to 50 keV energy range to be used for radioisotope dating with a small cyclotron

Abstract

represents that its use would not infringe privately owned ir^hls. Refer ence herein to any specific commerrial product, process, or service by trade name, itadcmark, manufacturer, or otherwise docs not necessarily oonstntute or nraply Els endorsement, recom mendation, ' &T favoring by 4he United States Government or any agency thereof. The views and ocanions-ctf authors expressed herein do ac& tKoessaTal}' suit or nfleci those cf the United Stales Gcnvmmcr.i or any agency ihcrcof. MASTER BlSTfiiBUTIOH OF THIS DOCUMENT IS UNLIMITED 3.3. Ion-signal pulse-height distribution 27 3.3.1. Effects of ion species, incidence angle, and energy on secondary-electron yield 3.4. Dark-noise and background pulse-height distributions and rates 3.4.1. Reducton of background by discrimination 3.4.2. Dark-noise stability 3.4.3. Sources of dark noise 3.5. Ion-counting efficiency versus dark-noise and background rates 3.5.1. Other criteria for choosing microchar.nel-plate voltage 3.6. Stability of gain, signal, and background after exposure to high currents or air 3.6.1. Experience and suggestions about exposure to air 3.7. Damage to electron multiplier from high-voltage discharge 3.7.1. Precautions to prevent damage 4. Operating ranges 4.1. Dynamic range and upper limit on anode current 4.2. Recovery time, maximum background rate, and low-energy background suppression 54 4.3. Ion-beam size and incidence angle 55 4.4. Operating pressures 56 4.5. Sensitivity to magnetic fields 57 4.6. Uniformity of response over microchannel plate and dynode surfaces 59 5. Conclusion 61 References 63 ion detector, and he gave me the opportunity to be eclectic in graduate school. Terry Mast lightened my load with insightful discussions and helped me to see the forest through the trees when I had lost my way. Luis Alvarez taught me to be sure of where I am headed and to report what I see clearly. Maynard Michel generously loaned me the use of an entire lab, including the wonderful mass separator he built, while I assembled and tested the detector. More important, he gave me the benefit of his time, knowledge,and experience from which I learned daily. Saul Perlmutter traveled this road beside me from the beginning to the end. He is a good listener and a fine companion. Ed Eberhardt answered countless questions about microchannel plates. Leonard Dietz provided critical information about secondary-electron emission. My parents had faith in me and encouraged me to find my own way. My daughter Erica put up with seeing me less than she wanted and greeted me joyfully when I came home. Most of all I thank Suzanne, for walking with me when the road is rocky. A Low Background-Rate Detector for Ions in the 5 to 50 keV Energy Range to be Used for Radioisotope Dating with a Small Cyclotron

Development of Radiocarbon Dating in China Over the Past 50 Years

“…After the re-introduction of the cyclotron AMS in 1977, a small cyclotron by the name "Cyclotrino" with a uniform magnet was initiated by the R A Muller group at Berkeley. Unfortunately, the Cyclotrino, after having been explored for 2 versions (Bertsch 1987;Friedman 1987;Welch 1987), failed to achieve acceptable 14 C counting. It was said that the Cyclotrino had been moved to another laboratory of Berkeley for its third version, called CMS with a uniform permanent magnet (Young et al 1993), on which no further report was seen.…”

A small low energy cyclotron for radioisotope measurements

“…This angle reduces its area of 19mm by 13mm to a projected area of about 4 mm by 13 mm which should provide a good match to the extracted beam size. At this angle, an average of 53 about 17 secondary electrons should be liberated by an incident ion; the peak of the distribution should be at 10 to 15 electrons (Friedman, 1986).…”

“…ions (Friedman, 1986;Friedman eta/., 1988). This detector uses an aluminum oxide conversion dynode which is impacted by the extracted ions at glancing incidence.…”