Attachment_A_-_Compton_Requirements_Document.pdf

Attachment A – NIST Compton Suppression System Requirements Document

A. BACKGROUND

The National Institute of Standards and Technology (NIST) Physical Measurement Laboratory (PML)

Radiation Physics Division (RPD) Radioactivity Group develops and improves the metrological techniques used for the standardization of radionuclides, and carries out a wide range of programs in low-level standards for environmental measurements and monitoring ,standards for nuclear medicine, standards and testing criteria for radiological instrumentation used for security, and radionuclide metrology.

A new impurity and activity measurement method is needed to determine short lived impurities in radioactive sources used for medical and industrial applications. The impurity measurements are critical for the primary standardization and calibration of radioactive materials. This new system will allow RPD to determine activity and detection limits with smaller uncertainties compared to the current High-purity Germanium (HPGe) detectors without the Compton suppression capabilities. The proposed acquisition is to obtain the required HPGe Compton Suppression System.

B. SCOPE

The RPD Radioactivity Group requires the purchase of a new Compton Suppression system. The required

Compton Suppression System shall be composed of the following parts:

HPGe detector

NaI annulus

Shielding with Cu/Sn liner

Digital electronics for both the HGPe and NaI detectors

Internal oscilloscope

Nitrogen purge port

Data acquisition system with required electronics and cabling

System installation

Specification for HPGe detector:

Minimum 50% relative efficiency

Maximum 2.1 keV resolution @ 1332 keV

Preamplifier

Ultra-Low-Background materials

30 Liter dewar

Required cables

Specification for NaI annulus (detector):

9" x 9" NaI Crystal

Maximum 9.5% energy resolution @ 662 keV

Four PMTs

Required connections

NaI Plug Detector, 3" x 3"

Specification for shielding:

Lead Shield

4" thick walls, Cu/Sn liner

N2 purge port

Nitrogen purge port:

N2 Gas Purge Kit

Electronics and data acquisition system:

Digital signal analyzer

High voltage power supply

Data acquisition system

Entire system cabling