Beam Dumping Ghost Signals in Electric Sweep Scanners
- SNS, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States)
- SNS, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA, 94720 (United States)
- Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)
Over the last 20 years many labs started to use Allison scanners to measure low-energy ion beam emittances. We show that large trajectory angles produce ghost signals due to the impact of the beamlet on the electric deflection plates. The strength of the ghost signal is proportional to the amount of beam entering the scanner. Depending on the ions and their velocity, ghost signals can have the opposite polarity as the main beam signals or the same polarity. These ghost signals are easily overlooked because they partly overlap the real signals, they are mostly below the 1% level, and they are often hidden in the noise. However, they cause significant errors in emittance estimates because they are associated with large trajectory angles. The strength of ghost signals, and the associated errors, can be drastically reduced with a simple modification of the deflection plates.
- OSTI ID:
- 20630796
- Journal Information:
- AIP Conference Proceedings, Vol. 763, Issue 1; Conference: 10. international symposium on production and neutralization of negative ions and beams, Kiev (Ukraine), 14-17 Sep 2004; Other Information: DOI: 10.1063/1.1908290; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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Ghost signals in Allison emittance scanners
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