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Jan 2003

Volume 74, Issue 1, pp. 1-912

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back to top PARTICLE SOURCES, OPTICS and ACCELERATION; PARTICLE DETECTORS

Characterization of a high-intensity unipolar-mode pulsed ion source with improved magnetically insulated diode

X. P. Zhu, M. K. Lei, Z. H. Dong, and T. C. Ma

Rev. Sci. Instrum. 74, 47 (2003); http://dx.doi.org/10.1063/1.1529303 (6 pages) | Cited 19 times

Online Publication Date: 16 January 2003

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A magnetically insulated ion diode (MID) with an improved external-magnetic field system has been developed and installed onto a TEMP-6-type high-intensity pulsed ion source in order to produce a high-intensity pulsed ion beam (HIPIB) for surface modification of materials. The external-magnetic field MID is operated in unipolar mode based on dielectric high-voltage flashover, and a double coaxial pulse-forming line (PFL) powered with a Marx generator is used to form the unipolar pulse of nanosecond width. A specially designed cathode has been constructed with a forked connection to two symmetrically installed transformers to improve the effect of the magnetic field and thus increase the stability of generation and propagation of the ion beam. It was found that the efficient generation of HIPIB mainly depended on the magnetic field strength, the gas pressures in reverse and output switches of PFL, and the anode–cathode (A–K) gap of the external-magnetic field MID. A proper magnetic field strength was found with magnetic field power system at dc charging voltage of 8 kV. The proper A–K gap distance is not uniform with the value varied from 6 to 8 mm. Suitable gas pressures for reverse and output switches were about 1.2 and 2.4 atm, respectively, at a charging voltage of 40 kV to the Marx generator. The most efficient plasma generation and ion extraction led to a maximum output of HIPIB with a peak ion current density of 300 A cm−2 and a beam pulse width of 80 ns (full width at half maximum), at an accelerating pulse of 300–350 kV with a pulse width of 70 ns. © 2003 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
52.59.Mv High-voltage diodes

Study of electron identification in a few GeV region by an emulsion cloud chamber

K. Kodama, K. Hoshino, M. Komatsu, M. Miyanishi, M. Nakamura, T. Nakamura, T. Nakano, K. Narita, K. Niwa, N. Nonaka, O. Sato, T. Toshito, and T. Uetake

Rev. Sci. Instrum. 74, 53 (2003); http://dx.doi.org/10.1063/1.1529300 (4 pages) | Cited 3 times

Online Publication Date: 16 January 2003

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We have performed an experimental study of electron identification using an emulsion cloud chamber detector with electron-enriched π− beams at 2 and 4 GeV/c produced by the proton synchrotron source at CERN. This study shows that the efficiency of electron identification is about 90% with little (6%) contamination from pions. These results are in agreement with those obtained using a Cherenkov counter and are reproduced well by the simulation. © 2003 American Institute of Physics.
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29.40.Gx Tracking and position-sensitive detectors
29.40.Rg Nuclear emulsions

256-anode channel plate device for simultaneous ion detection in time of flight measurements

S. Bouneau, P. Cohen, S. Della Negra, D. Jacquet, Y. Le Beyec, J. Le Bris, M. Pautrat, and R. Sellem

Rev. Sci. Instrum. 74, 57 (2003); http://dx.doi.org/10.1063/1.1527721 (11 pages) | Cited 8 times

Online Publication Date: 16 January 2003

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A 256-anode channel plate device with dedicated electronics has been built for the detection and accurate timing of a large number of simultaneous particle impacts in counting mode. In addition, a method is described which extends the performance of this detector by providing access to the amplitude response without any encoding. This experimental amplitude is extracted for each pixel using a threshold discriminator variation procedure. A detailed description of the detection processes allows calculation of the detector output signal amplitude for single as well as for multiple impacts per pixel. These calculations take into account the geometrical design of the pixelated anode structure. From a comparison between calculated and experimental amplitudes the number of incident particles per pixel can be deduced and thus the total number of particles impinging on the MCP surface. An illustration is given that uses the spatial distribution of swift C60 carbon constituents that exit a thin carbon foil. © 2003 American Institute of Physics.
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29.40.-n Radiation detectors
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors

Physics of the expanding plasma ejected from a small spot illumined by an ultraviolet pulsed laser

V. Nassisi and A. Pedone

Rev. Sci. Instrum. 74, 68 (2003); http://dx.doi.org/10.1063/1.1527202 (5 pages) | Cited 23 times

Online Publication Date: 16 January 2003

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We present the results concerning the physics of the expanding plasma produced by a laser ion source. An efficient source of multiple charged ions was realized by means of an excimer laser. The analysis of the generated plasma was performed for three different laser spot sizes, determining the threshold conditions of the ablation process for a Cu target. Two typologies of Faraday cups were developed in order to detect the plasma current and the ion current along the propagation tube. The time-of-flight measurements were performed inserting in front of the cup an adjustable voltage electrostatic barrier that allowed us to get quantitative information about the ion flux and the kinetic energy of the produced ions. To study the plasma characteristics we measured the total etched material per pulse, 0.25 μg, and the fractional ionization, 12%. The ablated material distribution was monitored by optical transmission analysis of a deposited film. Applying a high voltage to the extraction gap, an ion beam containing Cu+1 (0.44 mA), Cu+2 (0.34 mA), Cu+3 (0.09 mA), and Cu+4 (0.01 mA) ions was obtained. © 2003 American Institute of Physics.
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52.38.Mf Laser ablation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.-b Plasma properties
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