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Dotson, D.W.

Paper Title Page
RPAT100 Radiation-Hard Beam Position Detector for Use in the Accelerator Dump Lines 4341
 
  • P. Degtiarenko, D.W. Dotson, V.P. Popov
    Jefferson Lab, Newport News, Virginia
 
  Funding: This work supported by the U.S. Department of Energy under contract DE-AC05-84ER40150

The new proposed method of beam position measurement is particularly suitable for monitoring high energy, and high power accelerated beams of charged particles in the vicinity of power beam dumps. Generally, the beam quality in those areas is very poor, and any equipment positioned there must be extremely resistant to radiation damage. We have found that a plate made of Chemical Vapor Deposition (CVD) Silicon Carbide (SiC) has a set of physical properties that make it suitable for such an application. CVD SiC material is a chemically inert, extremely radiation-hard, thermo-resistive semiconductor capable of withstanding working temperatures up to 2000 degrees Kelvin. It has good thermal conductivity comparable to that of Aluminum, which makes it possible to use it in high-current particle beams. High electrical resistivity of the material, and its semiconductor properties allow characterization of the position of a particle beam crossing such a plate by measuring balance of electrical currents at the plate ends. The design of a test device, and first results are presented in the report.

 
RPPE064 Development of a Cryogenic Radiation Detector for Mapping Radio Frequency Superconducting Cavity Field Emissions 3627
 
  • D.W. Dotson, J. Mammosser
    Jefferson Lab, Newport News, Virginia
 
  Funding: Work supported by: U.S. DOE Contract No. DE-AC05-84er4015.

There is a relationship between field emissions in a Super Conducting RF cavity and the production of radiation (mostly X-rays). External (room temperature) detectors are shielded from the onset of low energy X-rays by the vacuum and cryogenic stainless steel module walls. An internal measuring system for mapping field emissions would assist scientists and engineers in perfecting surface deposition and acid washing module surfaces. Two measurement systems are undergoing cryogenic testing at JLab. One is an active CsI photodiode array and the second is an X-ray film camera. The CsI array has operated sucessfully in a cavity in liquid Helium but saturated at higher power due to scattering in the cavity. A shield with an aperature similar to the X-ray film detector is being designed for the next series of tests which will be completed before PAC-05.

 
RPPE065 Beam Loss Ion Chamber System Upgrade for Experimental Halls 3650
 
  • D.W. Dotson, D.J. Seidman
    Jefferson Lab, Newport News, Virginia
 
  Funding: Work supported by: U.S. DOE Contract No DE-AC05-84ER4015.

The Beam loss Ion Chamber System (BLICS) was developed to protect Jefferson Labs transport lines, targets and beam dumps from a catastrophic "burn through." Range changes and testing was accomplished manually requiring the experiment to be shut down. The new upgraded system is based around an "off the shelf" Programmable Logic Controller located in a single controll box supporting up to ten individual detectors. All functions that formerly required an entry into the experimental hall and manual adjustment can be accomplished from the Machine Control Center (MCC). A further innovation was the addition of a High Voltage "Brick" at the detector location. A single cable supplies the required voltage for the Brick and a return line for the ion chamber signal. The read back screens display range, trip point, and accumulated dose for each location. The new system is very cost effective and significantly reduces the amount of lost experimental time.