Low temperature calorimeters can be used to measure the energy released by a single particle with very high resolution. We have developed a system for studying the behaviour of various kinds of calorimeters from the point of view of their thermoelectrical properties and also their characteristics as particle detectors. Preliminary experimental results of a composite detector are shown (the resolution is 3% for the 8.78 MeV α-line from 228 Ra). Future developments both for optimizing the resolution and improving the system performances are briefly discussed.

Thermal detection of particles using bolometric devices

A new detector of ballistic phonons is presented It is a P‐doped Si bolometer realized on top of a (100)Si crystal by ion implantation The open circuit responsivity of the bolometer is 8000 V/W and the response time less than 50 ns Time‐resolved spectra of ballistic phonons propagating in the same Si crystal along the 〈100〉 direction are reported

Fast P‐doped silicon bolometer for detecting heat pulses

Low temperature calorimeters can be used to measure the total energy released in them by a single particle. Resolutions better than 1 eV are theoretically achievable with this kind of detectors. Preliminary experimental results in the range 80–1000 mK obtained with two different test detectors are reported. A reproducible process for the fabrications of high sensitivity thermistors is described. Future developments are briefly discussed.

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Heat capacity of low temperature Ge- and Si-calorimeters and optimazation of As-implanted silicon thermistors

The implementation of a 16‐channel, low‐temperature bolometer linear detector array is described. The detectors are silicon samples, whose surfaces are doped with phosphorus by the technique of ionic implantation. A single digital processor implemented on a common PC both provides the scanning of the array and performs synchronous signal detection from the different bolometers. The actual system has been tested with a broad infrared source, and some possible improvements are indicated.

Low‐temperature bolometer array

The temperature coefficient of resistivity (TCR) and cryogenic sensitivity (Sv) of p-type silicon (p-Si) in the low-temperature region (10–30 K) are remarkably improved by increasing the coverage of galvanically displaced Au nanoparticles (NPs). By increase of the galvanic displacement time from 10 to 30 s, the average surface roughness (Ra) of the samples increases from 0.31 to 2.31 nm and the coverage rate of Au NPs increases from 3.1% to 21.9%. In the freeze-out region of the sample, an up to 103% increase of TCR and dramatically improved Sv of p-Si (∼5813%) are observed with Au coverage of 21.9% compared to p-Si without galvanically displaced Au NPs. By means of a finite element method (FEM) simulation study, it was found that the increase of surface roughness and a number of Au NPs on p-Si results in a higher temperature gradient and thermoelectric power to cause the unusual TCR and Sv values in the samples.

F. Mori

Papers

Fast silicon p doped low temperature bolometer