Proposed new accelerator design for homeland security x-ray applications

Journal Article · Thu Jan 01 00:00:00 EST 2015 · Physics Procedia

DOI:https://doi.org/10.1016/j.phpro.2015.05.032· OSTI ID:1204542

Clayton, James ^[1]; Shedlock, Daniel ^[1]; Langeveld, Willem G.J. ^[2]; Bharadwaj, Vinod ^[3]; Nosochkov, Yuri ^[3]

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1. Varian Medical Systems, Palo Alto, CA (United States)
2. Rapiscan Laboratories, Sunnyvale, CA (United States)
3. SLAC National Accelerator Laboratory, Menlo Park (United States)

Two goals for security scanning of cargo and freight are the ability to determine the type of material that is being imaged, and to do so at low radiation dose. One commonly used technique to determine the effective Z of the cargo is dual-energy imaging, i.e. imaging with different x-ray energy spectra. Another technique uses the fact that the transmitted x-ray spectrum itself also depends on the effective Z. Spectroscopy is difficult because the energy of individual x rays needs to be measured in a very high count-rate environment. Typical accelerators for security applications offer large but short bursts of x-rays, suitable for current-mode integrated imaging. In order to perform x-ray spectroscopy, a new accelerator design is desired that has the following features: 1) increased duty factor in order to spread out the arrival of x-rays at the detector array over time; 2) x-ray intensity modulation from one delivered pulse to the next by adjusting the accelerator electron beam instantaneous current so as to deliver adequate signal without saturating the spectroscopic detector; and 3) the capability to direct the (forward peaked) x-ray intensity towards high-attenuation areas in the cargo (“fan-beam-steering”). Current sources are capable of 0.1% duty factor, although usually they are operated at significantly lower duty factors (~0.04%), but duty factors in the range 0.4-1.0% are desired. The higher duty factor can be accomplished, e.g., by moving from 300 pulses per second (pps) to 1000 pps and/or increasing the pulse duration from a typical 4 μs to 10 μs. This paper describes initial R&D to examine cost effective modifications that could be performed on a typical accelerator for these purposes, as well as R&D for fan-beam steering.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC03-7600-515
• OSTI ID: 1204542
• Journal Information: Physics Procedia, Vol. 66, Issue C; ISSN 1875-3892
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
High duty factor
accelerator
x-ray
spectroscopy
beam current modulation
material discrimination