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In this paper, the design and test results of a front-end cryogenic amplifier for a bolometer detector are presented. The amplifier is implemented with two low-noise Si JFETs, where the first FET is configured as a source follower amplifier and the second FET provides a high dynamic resistance to keep the voltage gain very close to unity. A 3 dB bandwidth over a wide range from DC to 10 MHz is achieved in this design. The input voltage noise density is ~ 1.9 nV/√Hz at 300 K, which further reduces to 1.6 nV/√Hz at 120 K. The flicker corner frequency observed is below 50 Hz. [ABSTRACT FROM AUTHOR]

Systematic studies with a sapphire bolometer test setup, made with indigenously made NTD Ge sensor, are carried out. A C++ and ROOT-based pulse analysis program implementing Savitzky–Golay filtering technique for analyzing the bolometer signal is discussed. Response of the bolometer subject to heater pulses of energy equivalent of 0.3–5 MeV is presented in the temperature range of 10–100 mK. The energy resolution is found to be 15 ± 3 keV in the temperature range of 15–25 mK. It is observed that the energy resolution of the bolometer is nearly constant ∼ 15 ± 3 keV over the energy range of 0.3–5 MeV. Performance of the bolometer with the addition of a moderate-size tin sample (∼ 0.6 g) to the sapphire substrate is presented. The impact of vibration on the bolometer is also discussed. [ABSTRACT FROM AUTHOR]

This paper reports the detailed noise characterization, investigation of various noise sources, and its mitigation to improve the performance of a cryogenic bolometer detector for the TIN.TIN experiment. The noise spectrum has been measured for a sapphire bolometer test setup with an indigenously developed neutron transmutation doped Ge sensor in the cryogen free dilution refrigerator system at Mumbai. The effect of external noise, arising either from ground loops in the system or from the diagnostic and control electronics of the cryostat, on the performance of the bolometer is assessed. A systematic comparison of the influence of different noise pickups on the bolometer resolution is also presented. The best-achieved resolution (σE) at 15 mK is ∼15 keV for heater pulses and appears to be mainly limited by the noise due to the pulse tube cryocooler. [ABSTRACT FROM AUTHOR]

Neutron transmutation-doped (NTD) Ge sensors have been prepared by irradiating device-grade Ge with thermal neutrons at Dhruva reactor, BARC, Mumbai. These sensors are intended to be used for the study of neutrinoless double beta decay in $$^{124}$$ Sn with a superconducting Tin bolometer. Resistance measurements are performed on NTD Ge sensors in the temperature range 100-350 mK. The observed temperature dependence is found to be consistent with the variable-range hopping mechanism. [ABSTRACT FROM AUTHOR]

A calorimeter set up with very low heat capacity ( $$\sim $$ 20 nJ/K at 100 mK) has been designed using commercial Carbon based resistors. This calorimeter is used to determine the heat capacity of small samples of superconducting bolometer absorbers. In particular, we present heat capacity studies of Tin, a bolometer candidate for Neutrinoless Double Beta Decay in $$^{124}$$ Sn, in the temperature range of 60-400 mK. [ABSTRACT FROM AUTHOR]

The feasibility study for searching neutrinoless double beta decay in 124Sn using cryogenic bolometer has been initiated. For this purpose, a custom-built cryogen-free dilution refrigerator, having a large cooling power of 1.4 mW at 120 mK, has been installed at TIFR, India. This paper describes the design, installation and performance of a cryogen-free dilution refrigerator (CFDR-1200). The performance of CFDR-1200 has been analysed using Takano’s model developed for conventional (wet) dilution refrigerators. [ABSTRACT FROM AUTHOR]