1. Calibration of uniformity between LYSO crystals Zhigang Wang Institute of High Energy Physics, CAS 2016.01.20 The Third International Workshop on the High Energy cosmic-Radiation Detection 1

2. Outline 1, LYSO performance test from a 137 Cs source 2, Calibration results from pions beam 3, Exploited LYSO intrinsic background for calibration purposes 2

3. 3 1, LYSO performance test from a 137Cs source

4. Intrinsic background of LYSO crystal LYSO= Lu2(SiO4)YO:Ce Lutetium based scintillator 175Lu Stable: 97.4% 176Lu Radioactive: 2.6% LYSO crystal contains a fraction of the naturally occurring isotope 176Lu, which undergoes β- decay followed by the emission of 88,202and 307 keV gamma rays causing signals which can cause phosphorescene. 4 Decay chain of 176 Lu Spectrum of LYSO intrinsic background 597 keV

5. Test setup in laboratory In the measurement, one face of the LYSO crystal was coupled to PMT(XP2020) with an air gap, while all other faces were wrapped with ESR reflector. 5 Data acquired by DT5751. The DT5751 is a 2-4 Channel 10 bit 2/1 GS/s Desktop Waveform Digitizer with self trigger.

6. LYSO irradiation with 137 Cs source 6 1: Background(Red) 2:Background + 137 Cs(blue) 137 Cs Spectrum: [1]-[2] Limited by the transfer rate of the DT5751, only the high energy events are selected by set a proper energy threshold. Light output and resolution results used to selected crystals.

7. Relative light output of 250 LYSO cubes 250 LYSO crystals were selected from 260 pieces. The difference of light output of 250 LYSO is ~25%, as shown in figure. The difference of six sides of one LYSO crystal cube is little than 4%. 7 Crystal number Light output

8. Energy resolution of 250 LYSO cubes The energy resolution of the 250 LYSO crystals we selected is <5%. 8 Crystal number σ/E

9. 9 2, Calibration results from pions beam

10. During the beam test at CERN, we carried out Pion(50GeV/c) calibration four times. The forth calibration data is significantly larger than other three. 10 Pion calibration results Pion calibration-1 Pion calibraton-2 Pion calibration-3 Pion calibraton-4

11. Variation of the calibration 11 Select second set of data as standard, compare calibration data which from the same crystal. For the same piece of crystal, the calibration result shows up an increasing trend. Very preliminary result Pion calibration-1 Pion calibraton-2 Pion calibration-3 Pion calibraton-4

12. 12 3, Exploited LYSO intrinsic background for calibration purposes

13. ICCD readout system of HERD 13 The image intensifier has two roles in the readout system: electronic shutter and signal amplifier.

14. LYSO intrinsic background image 14 The energy deposited by MIP in HERD LYSO crystal is about 30 MeV, the highest peak of intrinsic background from LYSO is about 600 keV. In the normal data taking mode, the image intensifier worked with proper gain: the ICCD can detect MIP, while the intrinsic background will have no influence on it. If adjust the image intensifier with higher gain, the intrinsic background will produce signal in ICCD. Fiber distribution Intrinsic background image in ICCD

15. LYSO intrinsic background signal 15 The intrinsic background signal with different image intensifier gain.

16. 16 Compared with Pion calibration The intrinsic background and pion calibration results. Pion calibration-1 Pion calibraton-2 Pion calibration-3 Pion calibraton-4 LYSO background

17. 17 To a certain degree, the intrinsic background of LYSO can be used as a complementary calibration method. The accuracy of LYSO intrinsic background calibration need to improved. Compared with Pion calibration Pion calibration-1 Pion calibraton-2 Pion calibration-3 Pion calibraton-4 LYSO background Very preliminary result

18. Radiation damage of LSO and YSO under 24 GeV protons 18 E. Auffray, A. Borisevitch, A. Gektin, et al. E. Auffary, A.Barysevich, A. Fedorov, et al. “Heavy charged particles, such as protons, hadrons, or nuclear fragments, lose much more energy and generate a shower of displaced ions in the crystal. A set of radioisotopes is created in the crystal.”

19. Radiation damage of LYSO 19 LYSO background during beam test LYSO background before beam test This may be one of the reasons why the calibration and resolution results are not good as expected. We need to work even harder! We can expect that after LYSO crystals interacting with heavy charged particles, will also create a set of radioisotopes. One of the main consequences of radiation damage in LYSO crystals is the induced phosphorescence.

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21. Peak position at 12030 ADC MIP energy ~ 375 p.e. 21