Phonon-Mediated Distributed Transition- Edge-Sensor X-ray Detectors Steven W. Leman Department of Nuclear Engineering and Management, The University of Tokyo LTD-12 August 2007

2 Important People Paul Brink Blas Cabrera Astrid Tomada Betty Young

3 Goals, applications and detector basics Energy systems, charge traps and neutralization 2-d Si 2-d Ge 2-d Si with deep trenches Energy Resolution Overview

4 Scientific Motivation Galaxy cluster surveys Warm-hot intergalactic medium

5 Performance Goals 2 dimension resolving 1-10 keV band Position resolution x/  x and y/  y ~ 100 Energy resolution E/  E ~ 1000 Large area ~1-10 cm 2 –Via 30 x 30 multiplexed arrays –Equivalent to a 10 megapixel device

6 Phonon Mediated Detector L.E.D.

7 3 Detector Comparisons Ge … ½ Si Debye freq   TES reduced by ½

8 Detector with Source 1cm 2cm that little spot is the 4 transition edge sensors refrigerator cold stage x-ray source

9 Position Determination Resolution ~20  m.

10 Spectra Silicon Germanium Silicon deep trench

11 Energy Absorption SiliconGermaniumSilicon deep trench Silicon complete trench Thickness [  m] Trench depth [  m] 220 (63%) 275 (50%) 320 (91%) 350 (100%) Energy absorbed [keV] 2.9 (49%) ~ (70%) 4.5 (76%)

12 Energy Losses Energy resolution is degraded due to energy going into nondetectable channels. –Electron—hole pairs lost in charge traps. –Electron—hole pairs diffuse through bridge and lost to the environment. –Phonons escape through bridge and lost to the environment.

13 Electron-hole number variation X-rays absorbed  electron—hole pairs produced. F = 0.116, Fano factor. E  = 5.9 keV, X-ray energy.   = 3.8 eV, electron-hole production energy.

14 Phonon energy variation The electron—hole pairs shed energy until they reach the velocity of sound. E gap = 1.2 eV, electron-hole gap energy.

15 Full-Width at Half-Maximum  det ~ 0.5, detection efficiency to convert to FWHM.

16 Combined with baseline noise Baseline noise = 37 eV. 68% of energy initially goes into phonons. 76% could be absorbed in completely trenched TESs. Could this suggest the electron—hole pairs are not releasing their energy in the detector?

17 Trap Concentrations Penn / Dougherty –8,000  cm –10 13 traps / cm 3 Us –10  cm –10 16 traps / cm 3