Ultra Low-background HPGe Detectors

DESCRIPTION

Design

• Task related design (U-type, vertical, down-looking or portable cryostat)
• Remote not cooled part of preamplifier
• Zeolite is placed near not cooled part of preamplifier in order to be outside measuring chamber

Cryostat materials

• Certified materials with low radiation impurities
• Ultrapure aluminium–silicon alloy with U + Th content < 1, 0.5 or 0.2 ppb for detector holder and endcap
• Freshly produced electrolytic copper for coldfinger an pedestal
• Tested on radiopurity selected stainless steel screws and sapphire insulators

Technology

• Transportation of HPGe crystal and cryostat materials by surface freight
• Minimization of fabrication time (location of materials above ground)
• Assembly in a cleanroom
• Cleaning and passivation of copper surfaces
• Storage of crystal and cryostat materials in a container made from materials effectively slowing down and absorbing neutrons (water and Cd)

Design features

• Fabrication of large volume HPGe detectors without bulletization
• Front end electronics made on low-background Teflon substrate
• Passive screen between front end electronics and HPGe crystal made from Pb with Bi-210 radioactivity < 0.1 Bq/kg
• Double-crystal HPGe detector design
• Multi-crystal HPGe detector design