Hard X-ray and low-energy gamma-ray spectrometers

Abstract

Basic principles of operation and characteristics of scintillation and semi-conductor detectors used for solar hard X-ray and gamma-ray spectrometers are presented. Scintillation materials such as NaI offer high stopping power for incident gamma rays, modest energy resolution, and relatively simple operation. They are, to date, the most often used detector in solar gamma-ray spectroscopy. The scintillator BGO has higher stopping power than NaI, but poorer energy resolution. The primary advantage of semi-conductor materials such as Ge is their high-energy resolution. Monte-Carlo simulations of the response of NaI and Ge detectors to model solar flare inputs show the benefit of high resolution for studying spectral lines. No semi-conductor material besides Ge is currently available with adequate combined size and purity to make general-use hard X-ray and gamma-ray detectors for solar studies.

Solar X‐Ray Physics

“…The rise time of the x‐ray bursts are consistent with the thermal conduction front model [ Batchelor , 1989]. However, the differences between most of the correlations derived from the different hard x‐ray interpretations were insufficient to establish a preference between the thermal and thick‐target processes [ Starr et al , 1988].…”

“…Reviews of specific flare topics include the impulsive phase [ Dennis , 1988; Dennis and Schwartz , 1989], multispectral observations [ Walker; 1988], soft x‐ray line emission [ Doschek , 1990], comparisons between solar and stellar flares [ Haisch , 1989b; Mullan , 1989], theories of particle acceleration [ Vlahos , 1989], loop models [ Emslie , 1989], directivity of hard x‐ray and gamma‐ray emission [ Kane , 1987; Vestrand , 1988], lack of observed x‐ray polarization [ Chanan et al , 1988], relations between hard x‐rays and microwaves [ Crannell et al ,1988], and various aspects of flares [ Rust and Batchelor , 1987; Ramaty et al , 1988]. Many of these reviews include discussions of new instruments and the scientific requirements for these instruments (see also Gehrels et al , [1988]).…”

Modulation transfer function analysis of silicon X-ray sensor with trench-structured photodiodes

“…In X-ray sensors, an indirect X-ray detection type using a scintillator has been developed, but even the NaI scintillator with high absolute fluorescence efficiency possesses the efficiency value of only 13% [1].…”

Silicon trench photodiodes on a wafer for efficient X-ray-to-current signal conversion using side-X-ray-irradiation mode

“…However, even for a NaI (Tl) scintillator showing high absolute fluorescence efficiency, this value is only about 13%. 3) For anthracene, the absolute fluorescence efficiency is 5%. 4) For Y 2 SiO 5 and Lu 2 SiO 5 , the absolute fluorescence efficiency is 10% or less.…”