Improvements to the Leake neutron detector II: Extension to 10GeV energy

Improvements to the Leake neutron detector III: Increased sensitivity and compliance with ANSI and IEC standards

“…In addition to the references given in [1,3] we note that Bhuiya et al [9] have developed a spherical detector with a number of thermoluminescent dosemeters (TLDs) at different levels that enables a good H n (10) response to be obtained but this would not readily lead to a real time monitor. Tanner et al [10][11][12] have developed a spherical polyethylene moderator detector with guide tubes to improve the thermal response and they have progressively improved their designs.…”

“…The only practical way of further increasing the sensitivity, without sacrificing the energy response, is to either increase the 3 He pressure in the SP9 or to increase the size of the spherical proportional counter. The SP9 is a very good design based on the counters that were developed for neutron spectrometry in reactors using hydrogen filled spherical proportional counters.…”

“…In general the MCNP calculations were carried out with the neutrons incident at 1801 to the connector using a disk source of 104 mm radius, 300 mm from the centre of the sphere. We have previously discussed [3] the errors in polar response but for practical purposes the detector has an isotropic response. Of course the addition of any electronics to make a portable monitor will modify the polar response.…”

“…A full discussion of the effect of gamma radiation has been given in [3] and the historical reason for using Kr is given in [3]. Effectively these detectors have a rejection ratio of better than 3000:1 for gamma energies from 3 to 7 MeV (i.e., including 16 N gamma rays) at dose rates up to 10 mSv/h.…”

“…It is referred to as NGREM (2004) in this paper (see also Table 1). In paper II [3] we described how the energy response could be extended to the GeV region by including a lead collar around the SP9 spherical 3 He detector at the centre of the spherical moderator. However, in order to get a good energy response over the extended energy range, it was necessary to increase the diameter of the outer polyethylene sphere to 240 mm giving an overall weight (including lead) of 7.9 kg (this is the SNS-LINUS detector).…”