N3C2  Radiation Damage Effects

Wednesday, Nov. 4  14:00-16:00  San Diego

Session Chair:  Vitaliy Fadeyev, UCSC, United States; Giovanni Calderini, Laboratoire de Physique Nucleaire et des Hautes Energies, Paris and Pisa University, France

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(14:00) N3C2-1, Measurements and TCAD Simulations of Bulk and Surface Radiation Damage Effects

F. Moscatelli1,2, D. Passeri3,2, G. M. Bilei2, A. Morozzi3,2, G.-F. Dalla Betta4,5, R. Mendicino4,5, M. Boscardin6, N. Zorzi6, L. Servoli2, P. Maccagnani1

1IMM-CNR Bologna, Bologna, Italy
2INFN Perugia, Perugia, Italy
3Dept. of Engineering, University of Perugia, Perugia, Italy
4DII, University of Trento, Trento, Italy
5TIFPA-INFN, Trento, Italy
6Fondazione Bruno Kessler (FBK), Trento, Italy

In this work we propose the application of a radiation damage model based on the introduction of deep level traps/recombination center suitable for device level numerical simulation of radiation detectors at very high fluences (e.g. 1÷2×1016 1 MeV equivalent neutrons per square centimeter) combined with a surface damage model developed by using experimental parameters extracted from measurements carried out on gamma irradiated p-type dedicated test structures. The simulated electrical characteristics of irradiated detectors have been compared with experimental measurements, showing a very good agreement in terms of steady-state parameters (variation of depletion voltage, increase of the leakage current, electric field distribution) and in particular in terms of variation of the CCE as a function of the fluence. Oxide-charge density (Nox) and the interface-trap density (Dit) near the valence band extracted from the measurements after gamma irradiation are introduced in the model in order to develop a comprehensive bulk and surface damage model. This model should be therefore used as a predictive tool for investigating sensor behavior at different fluence, temperature, and bias voltage and will be used for the optimization of 3D and planar silicon detectors for future HL-LHC High Energy Physics experiments.

(14:20) N3C2-2, Proton Induced Radiation Damage in Fast Crystal Scintillators

F. Yang1, L. Zhang1, R.-Y. Zhu1, J. Kapustinsky2, R. Nelson2, Z. Wang2

1California Institute of Technology, Pasadena, CA 91125, USA
2Los Alamos National Laboratory, Los Alamos, NM 87545, USA

This paper reports charged hadron induced radiation damage in fast crystal scintillators irradiated by protons of 800 MeV, 64 MeV and 24 GeV respectively at the WNR facility of LANSCE, UC Davis and CERN. A 20 cm long LYSO crystal, a 15 cm long CeF3 crystal and four liquid scintillator based sealed quartz capillaries were irradiated to the level of 1014 p/cm2 at Los Alamos. Five and four LYSO plates of 14×14×1.5 mm3 were irradiated up to 9.5×1013 and 6.9×1015 p/cm2 respectively at UC Davis and CERN. No degradation is observed in both transmittance and light output in the LYSO plates after irradiations by 64 MeV and 24 GeV protons up to 1014 p/cm2. The radiation induced absorption coefficient value at 430 nm is found to be about 3 m-1 after a fluence of 3×1014 p/cm2, indicating excellent radiation hardness of LYSO crystals against charged hadrons. A good agreement is also found between light output degradations caused by protons and ?-rays. The results provide important information for understanding charged hadron induced radiation damage in these crystals.

(14:40) N3C2-3, Tests of the Signal from Minimum Ionising Particles of 50µm Thick Silicon Micro-Strip Sensors after Extreme Fluences above 3x1016 Neq Cm-2.

S. Wonsak, G. Casse, M. Milovanovic, P. Dervan

Dep. of Physics, O. Lodge Lab., University of Liverpool, Liverpool, UK

The development of silicon detectors tolerant to extreme fluences for future high energy and high luminosity hadron colliders (like the upgrade of the present Large Hadron Collider to high luminosity at CERN) is demanded not only for instrumenting the innermost layers (where pixel sensors will be deployed) but also for particle flow calorimetry. The anticipated fluence levels range from 2x1016 neq in the inner pixel layers to possibly 1x1017 neq cm-2 in the forward calorimeter region. The challenge is daunting, because of the large increase of the reverse current and the severe decrease of the signal recorder by the irradiated devices. The use of thin silicon detectors in charge multiplication regime could take the tolerance of silicon detectors further towards satisfying this requirement. We show here the experimental result obtained with silicon micro-strip sensors with a thickness of 50 µm irradiated with neutrons to various fluences up to 3x1016 neq cm-2. After irradiation the signal is studied with fast electrons from a radioactive source, to mimic the signal of minimum ionising particles. The sensors are readout with LHC speed electronics (the ALIBAVA system, 40MHz clock speed).

(15:00) N3C2-4, Drift Mobility and Electric Field in Silicon Detectors Irradiated with Neutrons and Protons up to 1E17 N_eq/cm^2

M. Mikuz1,2, V. Cindro2, G. Kramberger2, I. Mandic2, M. Zavrtanik2

1Physics Dept., Univ. Ljubljana, Ljubljana, Slovenia
2Experimental Particle Physics, Jozef Stefan Institute, Ljubljana, Slovenia

Electric field in silicon irradiated with neutrons up to 1e17 n_eq/cm^2 was investigated by edge-TCT. Methods for absolute determination of electric field were developed. From the v(E) dependence mobility degradation with fluence was extracted. A simple field structure was observed, consistent with a SCR and "ENB", a region that does not contribute to leakage current and the electric field there is consistent with current transport across highly resistive silicon. The observed mobility change and the values of electric field indicate substantial reduction of trapping from linear extrapolation of low fluence values. An irradiation campaign at CERN IRRAD covering the fluence range from 3e14 n_eq/cm^2 to 3e16 n_eq/cm^2 shall provide complementary information on electric field and mobility changes after charged hadron irradiation.

(15:20) N3C2-5, Neutron Irradiation Test of the Fine Pixel CCD Vertex Detector for the ILC

A. Ishikawa1, S. Murai1, S. Ito1, A. Dubey1, T. Horiguchi1, E. Kato1, J. Strube1, I. Ushiki1, S. Watanuki1, S. Yamaguchi1, H. Yamamoto1, C. Calancha2, A. Miyamoto2, Y. Sugimoto2, Y. Yasu2, H. Ikeda3, H. Sato4

1Tohoku University, Sendai, Japan
2High Energy Accelerator Research Organization (KEK), Tsukuba, Japan
3Japan Aerospace Exploration Agency (JAXA), Sagamihara, Japan
4Shinshu University, Matsumoto, Japan

Fine Pixel CCD (FPCCD) is one of the candidate vertex detectors for the ILC. The FPCCD provides most precise intrinsic position resolution with 5um pixels among the candidates. However neutron tolerance of the FPCCD was not well studied and some degradation of performance was expected. We had a neutron irradiation test using 6x6mm2 small prototype FPCCD made by Hamamatsu Photonics at CYRIC at Tohoku University. Almost monochromatic neutron beam, whose energy is about 65MeV, was produced from 70MeV proton beam with Li + p --> Be + n reaction, and irradiated to the FPCCD. The 1MeV equivalent neutron fluence was estimated about 1.8x1010 neq/cm2 with NIEL assumption which corresponds to about 19 year operation at ECM=500GeV at the ILC. We measured performance of the FPCCD, such as dark current, hot pixel and charge transfer inefficiency, before and after the neutron irradiation. We saw performance degradation however we can calibrate the degradation effect at offline and this will not make a serious problem on tracking and vertexing. Thus we concluded that the neutron background at ECM=500GeV at the ILC is no problem for the FPCCD vertex detector.

(15:40) N3C2-6, Gamma-Ray Induced Radiation Damage up to 200 Mrad in Various Scintillation Crystals

F. Yang, L. Zhang, R. Zhu

Crystal Lab, HEP, California Institute of Technology, Pasadena, USA

Because of their superb energy resolution and detection efficiency scintillation crystals are widely used in high energy physics experiments. One crucial issue, however, is crystal’s radiation damage. We report an investigation on ?-ray induced radiation damage in fast crystal scintillators of large size, including BaF2, BGO, CeF3, pure CsI, LSO/LYSO and PWO, with an integrated dose up to 200 Mrad and a dose rate up to 1 Mrad/h. Optical and scintillation properties of these crystal samples were measured before and after ?-ray irradiations. The result shows that pure LYSO and pure CsI crystals have good radiation hardness below 10 krad. LYSO, BGO and BaF2 crystals have good radiation hardness beyond 1 Mrad. In terms of light output degradation LYSO crystals are the best among all scintillation crystals.