Linearity with dose rate of low resistivity p-type silicon semiconductor detectors

Abstract

Semicondunor detectors based on ptype silicon but with different doping levels have been investigated. The linearity response with dose rate (dose per pulse in a pulsed beam). the sensitivity drop and the sensitivity variation with temperature have been investigated prehdiation, radiation damage, in different radiation qualities. It was shown that a p-type detector with a low doping lev& high resistivity, showed a non-linear dose rate response if radiation damaged in a high energy photon beam, which contains neuImns. By increasing the doping level it was shown that a detector with a resistivity of 03 Oan stay& linear after preirradiation in radiation fields from high energy elech.ons, photons and protons. Other parameters did not show any changes of clinical importance ai the dilYerent doping levels.

Dosimetric characteristics of an unshielded p-type Si diode: linearity, photon energy dependence and spatial resolution

“…However according to the literature [4,8,11,13,14], p-type silicon diodes show a slight supralinearity, only marginally detectable in plots like Fig. 2, but evident if the response is plotted versus pulse dose.…”

“…This is due to the energy expenditure per electron-hole pair of only 3.8 eV and the 2000 times larger mass density of silicon compared to the gas filling of ionisation chambers. The chance for an electron to escape recombination then increases with pulse dose [8], which leads to the effect shown in Fig. 3.…”

“…Furthermore, linear accelerators may be run in the high and low dose rate mode, involving microsecond pulses of radiation at varying repetition frequencies. Therefore, the linearity of the diode current versus the absorbed dose rate and the variation of the ''response'' of the diode -the quotient of diode current and dose rate -with pulse dose have to be tested [4,8,11,13,14]. Transversal scans of narrow photon fields may also involve gradual changes of the photon spectrum, so that the energy dependence of the diode response should be small [15].…”

Radiotherapy electron beams collimated by small tubular applicators: characterization by silicon and diamond diodes

“…For these reasons Si-D are well assessed in clinical relative electron dosimetry (Griessbach et al 2005, Evelin et al 1999, Rikner 1985. However, it is worth noting that a dependence of their response on beam energy, dose rate and radiation incidence angle has been reported in literature for some types of Si-D (Grusell and Rikner 1993, Björk et al 2000, Saini and Zhu 2004. Such a dependence can lead to incorrect dose evaluations in depth-dose and beam profiles measurements if appropriate correction factors are not applied (Song et al 2006).…”

Eigenschaften eines kommerziellen Hi-pSi-Detektors für die Dosimetrie stereotaktischer Kollimatoren mit sehr kleinen Durchmessern

“…Diese Forderung erfüllt der Diamantdetektor, der allerdings bei der Beschaffung erhebliche Kosten und Lieferprobleme verursacht. Alternativ werden seit einiger Zeit auch Halbleiterdetektoren auf der Basis von hoch dotiertem p-Typ-Silizium eingesetzt, die sich durch ihre Bauform und ihre Eigenschaften für diese Aufgabenstellung eignen sollen [4,6,9,10,12]. In dieser Arbeit wird ein speziell für stereotaktische Messungen entwickelter Siliziumdetektor der Firma Scanditronix untersucht, der sich durch einen vergleichsweise besonders kleinen Durchmesser auszeichnet.…”