Debuncher Profile Monitor Evaluation
The original microchannel plates have been damaged in the beam region. After an attempt to revive the plates by baking, the gain of the central 30mm is still reduced by approximately a factor of three. The plates appear to have been irreversibly damaged by being operated for an extended period of time at high gain with high debuncher beam currents. A new set of microchannel plates has been installed in the monitor. Because of a production error, the gap between the microchannel plate output and the anode wire plane was set at 15mm instead of 3mm. The high voltage divider allowed a maximum of 170 volts to be applied across this gap. Under the conditions at which the Monitor was being operated, the distribution of collected electrons from a single micro channel was spread over a large area. A collimated UV light source which had a FWHM of 3mm produced a profile with a FWHM of 22mm with an amplifier threshold supply voltage of 1.0 V and FWHM of 9mm with a threshold voltage of 5.0V. See Figure 1. When new microchannel plates were installed, the anode gap was reduced to 9.5mm, and the gap voltage was increased to 760V, the results shown in Figure 2 were obtained. The width of the distribution depends strongly on the plate gain and discriminator threshold. Analog readout with a SWIC scanner eliminates the dependence of width on plate gain. Figure 3 shows two scanner profiles with plate gains differing by a factor of 64. The anode wire plane allows a significant fraction of the charge to leak through into the low field region behind the plane and spread over several wires before being captured by the wires. This produces broad tails on the width distribution. Replacing the wire plane with strip electrodes etched on a printed circuit board eliminates this problem, as shown in Figure 4. Figure 5 shows scanner profiles with wire anodes and with P.C. strip anodes. The intrinsic resolution of the detector appears to be less than one element width (2.2mm), so the P.C. anode will have 8 elements instead of the previous 32. This will provide more useful information in measuring 1/2 {pi} beams from the booster.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 948900
- Report Number(s):
- FERMILAB-PBAR-NOTE-444; oai:inspirehep.net:244457; TRN: US200909%%277
- Country of Publication:
- United States
- Language:
- English
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