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LW Detector

General Specs

Thin lead sheet converts gamma rays to e plus / e minus pairs which create cherenkov radiation in the areogel in the head of the detector. A light tight 10 x 10 cm pipe lined with aluminium coated mylar guides the cherenkov radiation to a PMT at floor level (far from the beam level). The PMT is also shielded for additional protection. The detector is operated at 1250V and a 30 m heliax cable is used to relay the signal to the LW Hut where the signal is first attenuated and then digitised by a gated 14 bit ADC.

  • 7.3 mm lead (optimal thickness) - see LD's thesis
  • 4 x layers of 5 x 5 x 1 cm Aerogel - unknown whether single layer best
  • Hamamatsu R887
  • Typical attenuation 8 - 16 dB



Date Action
March 2012 Post earthquake check
Head rebuilt
Aerogel Holder rebuilt
Two photodiodes installed in head
September 2010 Rebuilt / Relocated
Relocated detector to immediately after B5FF
Rebuilt detector with additional horizontal arm at top
Reduced areogel area to 5 x 5 cm
Areogel original was 10 x 10cm - quartered and stacked this
Removed supporting base structure
June 2010 Head modification
Reduced lead area to 4 x 4 cm from 10 x 10 cm

Physics WebpagesRHUL WebpagesCampus Connect • Royal Holloway, University of London, Egham, Surrey TW20 0EX; Tel/Fax +44 (0)1784 434455/437520

Topic revision: r1 - 05 Nov 2012 - LaurieNevay

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