Xray and gamma ray spectrometers based on cadmium

X-ray and gamma ray spectrometers based on cadmium telluride detectors JSC “Institute in Physical-Technical Problems” is a branch company, specializing in the design and manufacture of spectrometers, detection units, and separate nuclear-physics instruments based on semiconductor and scintillation materials! JSC “Institute in Physical-Technical problems” 141980, Dubna, Moscow region, Kurchatova str. 4 Tel. : 8 49621 70645; fax 8 49621 65082 e-mail: iftp@dubna. ru http: //www. iftp. ru

For the diagnostics of physical processes in the nuclear-energetic installations of JSC IPTP a detection unit BDTK-1 K with the cadmium telluride detector with the area of 47 mm 2 and thickness 1. 1 mm and with thermoelectric cooling of the head module has been developed. The measuring results of the prototype of BDTK-1 K are given below. A digital signal processor (ЦСУ-B-1 K) developed at JSC IPTP was used for the detection unit testing.

Advantages of the cadmium telluride detectors • High atomic number (Z=50) and high density which implies high efficiency in gamma radiation detection; • Sufficiently large band gap width – 1. 5 e. V (that of silicon is 0. 9 e. V and of germanium is 0. 67 e. V) permitting to operate at room temperature with a low level of current noises; • Energy resolution is much better than that of scintillation detectors which allows one to use them for applications where a resolution of separate adjacent lines is required;

Specifications of the BDTK-1 K detection unit Detected energy range – from 5. 9 to 600 -1000 ke. V Energy resolution : by energy 5. 9 ke. V – 0. 62 ke. V; by energy 59. 6 ke. V – 0. 93 ke. V; by energy 122. 0 ke. V – 1. 5 ke. V; by energy 662. 0 ke. V – 6. 4 ke. V. Optimum operating voltage of SCD until minus 400 V. Optimum current of the cooler – 0. 7 A. Detection unit mass – 0. 87 kg. Overall size – 166× 106× 85 mm.

Relative efficiency of the detection depending on radiation energy Energy, ke. V 40. 5 46. 2 122. 08 244. 76 344. 14 410. 96 443. 66 779. 03 964. 43 1086. 44 1113. 04 1409. 15 counting reduced to output 100 % 4330591 5417770 1764669 277519 106646 73673 53616 10469 7225 3750 2338 1058 Fitting at Е > 100 ke. V count output % in peak 320463 58650593 7 39719066801830 2238059543518 285540 21480 104137 29221 61588 1665 49099 1705 9276 1340 4931 1026 3465 375 3226 311 1605 218 74 14. 8 30. 8 7. 74 27. 4 2. 26 3. 18 12. 8 14. 2 10 13. 3 20. 6 Starting from the energy Е>100 ke. V, the relative efficiency is well approximated by the following dependence: εотн=const / E-2. 96

Resolution-energy dependence Energy, Resolution, ke. V 40. 55 1. 375 46. 2 1. 599 122. 08 1. 679 244. 76 2. 703 344. 14 3. 551 410. 96 4. 522 443. 66 4. 678 779. 03 7. 025 964. 43 8. 748 1086. 44 8. 824 1113. 04 6. 401 1409. 15 8. 852

Fe-55 and Am-241 spectra 59. 54 ke. V Граница шумов – 1, 9 ke. V 5. 89 ke. V 13. 94 ke. V 26. 35 ke. V

Co-57 and Cs-137 spectra 32 ke. V 37 ke. V 122 ke. V Shaping time – 6 µs Lines 32 and 37 ke. V are K-alpha and K–beta series of the Ba-137 isotope generated at the Cs-137 decay. 662 ke. V

Spectrum of radioluminescence of the detectors 50 100 I, отн. ед. Scintillation detectors 400 450 §Density, g/cm 3. . . …. 1, 05 § Maximum of the luminescence spectrum, nm… 420 500 , нм

Scintillation detectors Designaiton Purpose T, ns ПС-Н 1 Detection of fast neutrons ПС-Б 2 Detection of fast neutrons and photon radiation with high time resolution высоким временным разрешением 0. 78 ПС-Б 3 same 1. 0 ПС-Б 4 same 0. 67 СПС-С 10 Detection of photon radiation due to photoeffect on lead atoms (up to 10% by mass) 1. 70 ПС-У 14 Detection of photon radiation using the automatic sensitivity control circuit

Summary Tellurid cadmium spectrometric systems are small in size and have a low power consumption. Cd. Te detection units are promising for use in portable instruments and stationary complexes of the technologic parameters control at nuclear power plants and allow one to substantially increase the operation characteristics in applied studies, radiography, and astrophysics. Detectors built with plastic scintillators have showed their advantage in radiation monitoring purposes.