The problem of achieving highest temperature difference /spl Delta/T in cascade thermoelectric cooler (TEC) is solved with consideration of intercascade thermal resistance. The model of ...three-dimensional heat spread in substrates is considered. Existence of substrate optimum thickness corresponding to highest /spl Delta/T is established. It is shown that correct choice of substrate configuration permits to receive considerable increase in TEC efficiency. In particular, it concerns short-legged TECs having extremely high heat flux densities.
Current \(\gamma\)-ray telescopes suffer from a gap in sensitivity in the energy range between 100keV and 100MeV, and no polarisation measurement has ever been done on cosmic sources above 1MeV. Past ...and present e\(^+\)e\(^-\) pair telescopes are limited at lower energies by the multiple scattering of electrons in passive tungsten converter plates. This results in low angular resolution, and, consequently, a drop in sensitivity to point sources below 1GeV. The polarisation information, which is carried by the azimuthal angle of the conversion plane, is lost for the same reasons. HARPO (Hermetic ARgon POlarimeter) is an R\&D program to characterise the operation of a gaseous detector (a Time Projection Chamber or TPC) as a high angular-resolution and sensitivity telescope and polarimeter for \(\gamma\) rays from cosmic sources. It represents a first step towards a future space instrument in the MeV-GeV range. We built and characterised a 30cm cubic demonstrator SPIE 91441M, and put it in a polarised \(\gamma\)-ray beam at the NewSUBARU accelerator in Japan. Data were taken at photon energies from 1.74MeV to 74MeV, and with different polarisation configurations. We describe the experimental setup in beam. We then describe the software we developed to reconstruct the photon conversion events, with special focus on low energies. We also describe the thorough simulation of the detector used to compare results. Finally we will present the performance of the detector as extracted from this analysis and preliminary measurements of the polarisation asymmetry. This beam-test qualification of a gas TPC prototype in a \(\gamma\)-ray beam could open the way to high-performance \(\gamma\)-ray astronomy and polarimetry in the MeV-GeV energy range in the near future.
A gas Time Projection Chamber can be used for gamma-ray astronomy with excellent angular-precision and sensitivity to faint sources, and for polarimetry, through the measurement of photon conversion ...to \(e^+e^-\) pairs. We present the expected performance in simulations and the recent development of a demonstrator for tests in a polarized photon beam.
A time projection chamber (TPC) can be used to measure the polarization of gamma rays with excellent angular precision and sensitivity in the MeV-GeV energy range through the conversion of photons to ...e+e- pairs. The Hermetic ARgon POlarimeter (HARPO) prototype was built to demonstrate this concept. It was recently tested in the polarized photon beam at the NewSUBARU facility in Japan. We present this data-taking run, which demonstrated the excellent performance of the HARPO TPC.
A method of evaluation of cascade thermoelectric cooler transient response is described. To check the theoretical model, experimental research on a wide range of single-stage and multi-stage TE ...coolers was carried out. Fast response coolers, providing an achievement of 90% of steady-state temperature difference for times from 1.2 to 6.2 s, have been developed. The limit speed of thermal response for cascade coolers is also predicted.
