The measurements were made using a 1980's era Eberline ESP-2 "Smart Portable" with the pulse height analysis option. The meter is shown in the image below. This instrument can serve as both a scaler and a ratemeter, the ratemeter option being used for the current measurements. High voltage can be varied from the user controls between 500 and 2450 volts. The PHA option allows a threshold and window to be set via trimmer potentiometers to isolate specific gamma-ray energies of interest. As an added bonus, the instrument can be controlled via a standard PC serial port.
The probe for the setup is a Teledyne Brown Engineering 7W8P2C1 shown below. This is a 2"x1.75" end-well scintillator with a 2" photomultiplier tube. The scintillation material is standard Thallium doped Sodium Iodide. The PMT base is a homemade affair based on a schematic for a Ludlum 44-10 probe. It uses positive high voltage and has a total dynode string resistance of about 63 Mohms. The probe base is attached to the instrument with a Ludlum 40-1011 cable with MHV connectors.
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Latest update: May 9, 2004 |