MainPage:Nuclear:Summer2014:PMTCharacterization

Abstract

The purpose of this project is to characterize large-diameter photomultiplier tubes (PMT) through scans along the surface of the PMT with a low-intensity, focused LED, thereby creating a plot of the surface area of the PMT with the gain at each section. Scanned PMTs can be better used in other testing because more is known about the gain across the entire front face, and thus if only a few photons need to be detected by the PMT, it can be better setup to detect those small amounts of light by positioning a spot with a higher gain in front of the source. The method of scanning said PMTs consists of a two axis step motor moving an LED light source on a 100 x 100 grid opposite the face of the PMT, with 30 pulses of light from the LED at each step. The step motor with a step of 1.8 degrees is moved 450 times each step resulting in a step length of… (need to figure out the thread size to calculate this). Scans conducted in this manner have a high enough resolution to pick up most sensitive/non-sensitive spots on a PMT including the three supports along the side of the PMT which support the dynodes and other components inside the PMT. While this method of scanning PMTs has been conducted in the past, including at The Catholic University of America, the current scanning method will be used to characterize a PMT from the University of Virginia.

Materials and Methods

Characterization of the following PMTs:

• Photonis Model XP4500/B, Serial 09641
• Photonis Model XP4572/B/D1
• Hamamatsu R1250 - https://www.hamamatsu.com/us/en/R1250.html
• University of Virginia PMT - Hamamatsu R1584 - http://www.hamamatsu.com/us/en/R1584.html

Other materials

• LED (need specification)
• Two axis motor - http://www.velmex.com/bislide_model_display.asp?id=19http://www.velmex.com/bislide_model_display.asp?id=19
• High Voltage Power Supply
• Coda programming to translate signal from PMT
• Anti-Magnetic Shielding
• Dark box and black cloth
• Optical fiber
• PS Octal 300 mHz Discriminator model 708
• PS Quad gate generator model 794
• Lecroy 2249A channel ADC http://www.fnal.gov/projects/ckm/jlab/2249a-spec.htm

Results

XP4500/B 09641

• 

  1589

• 

  1594

XP4572/B/D1

• 

  1597

• 

  1686

• 

  1691

• 

  1692

• 

  1696

• 

  1710

• 

  1719

Analysis

Results 1989 through 1692 were eschewed by the fact that the base used for those scans did not work correctly (labelled 5B). Once replaced by a different base (labelled 101), the XP4572/B/D1 scan came out approximately the same as the scans that Marco conducted earlier this year. Therefore, the problems with the initial scans cam most likely be accredited to the fact that the 5B base was not working correctly, perhaps because of it did not distribute the voltage correctly across all channels of the PMT.

Sources

Works Cited Hlavin, N. (n.d.). Kaon Aerogel Cherenkov. Washington, DC. Retrieved from http://www.jlab.org/Hall-C/talks/06_22_12/hlavin.pdf