Monitoring and control system for MPPCs for the upgraded koto CsI - PowerPoint PPT Presentation

Monitoring and control system for MPPCs for the upgraded koto CsI calorimeter Nobuhiro Hara 2017/12/28 Kuno and Yamanaka Group Year-End Presentation

KOTO EXPERIMENT 2 CsI ▸ Search for the rare decay (BR~3 × 10 -11 @SM) K L → π 0 ν ¯ ν ▸ Signal — 2 γ @CsI + nothing@other detectors

NEUTRON BACKGROUND 3 signal B.G. γ neutron CsI CsI π 0 K L γ ν ¯ ν ▸ Misidentify neutrons as photons. ▸ That B.G. was already reduced to 1/100 the Pulse shape cut. ▸ Furthermore, we need to reduce that B.G. by a factor 10.

BOTH-END READOUT SYSTEM 4 • Timing difference 
 → discriminate b/w photons and neutrons γ : Radiation length (~2cm) γ light CsI upper stream neutron : Interaction length (~40cm) neutron upper stream

BOTH-END READOUT SYSTEM 5 ▸ Current ▸ Both-end readout 500mm beam beam CsI PMT CsI PMT MPPC Large (50 × 50mm) Small (25 × 25mm) KOTO CsI calorimeter 25 50 25 50 Total 4096 MPPCs 4 MPPCs are connected → 1024ch

MONITORING & CONTROL SYSTEM 6 ▸ We need the system that monitor and control 1024ch MPPCs. ๏ Necessary function ✓ Monitor dark current of MPPCs 
 (to check that MPPCs are working normally 
 & to monitor the amount of radiation damage) ✓ Monitor & control high-voltage supplied to MPPCs ✓ Monitor temperature of the board ✓ Low power consumption

MONITORING & CONTROL SYSTEM 7 ▸ Overall picture of the system MPPCs × 16ch HV power Current Switch Supply ADC Sensor signal Switch Controller Temp Sensor ADC PC

CURRENT SENSOR 8 ▸ Design MPPCs current sensor AC coupling opamp 0.1uF 510 Ω LTC2055 signal + ADC 0.1uF 51 Ω - 510 Ω Signal of MPPC ~100ns

MONITORING DARK CURRENT 9 Requirement ➡ Large dynamic range(0-200uA) ▸ Dark current of MPPC 
 0.5uA(initially) → about 50uA(after irradiation) 
 4MPPCs are connected → ~200uA ▸ to measure I-V curve to check MPPCs 
 → need to measure small current(~0.01uA)

MONITORING DARK CURRENT 10 ▸ OPAMP(single power supply) can’t work well @ small current region ➡ Change to dual power supply Output of OPAMP (single/dual-power supply) Output[uV] 1600 1400 Red : single power supply +V +V Blue : dual power supply 1200 1000 + + 800 - - 600 GND 2 2 / ndf / ndf 0.03072 / 12 0.03072 / 12 χ χ 400 Prob Prob 1 1 p0 p0 14.62 14.62 24.16 24.16 ± ± single dual 200 p1 p1 2.249e+04 2.249e+04 674.7 674.7 ± ± 0 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 Current[uA]

MONITORING DARK CURRENT 11 ▸ I-V curve of normal MPPCs & irrad MPPCs I-V curve normal irrad Current[uA] Current[uA] 6 160 2 2 / ndf / ndf χ χ 5.993 / 21 5.993 / 21 2 2 χ χ / ndf / ndf 1.602 / 21 1.602 / 21 140 Prob Prob 0.9994 0.9994 Prob Prob 1 1 5 p0 p0 51.28 51.28 0.04245 0.04245 ± ± p0 p0 52.35 52.35 0.0205 0.0205 ± ± 120 p1 p1 0.2326 0.2326 ± ± 0.009034 0.009034 p1 p1 12.58 12.58 0.5331 0.5331 ± ± 4 p2 p2 0.002016 0.002016 0.001222 0.001222 ± ± p2 p2 0.008891 0.008891 0.003909 0.003909 − − ± ± 100 p3 p3 0.007587 0.007587 0.009394 0.009394 ± ± p3 p3 0.02205 0.02205 ± ± 0.009736 0.009736 3 80 60 2 40 1 20 0 0 50 51 52 53 54 55 56 50 51 52 53 54 55 56 Voltage[V] Voltage[V]

SUMMARY 12 ▸ We will install 4096 MPPCs to reduce the neutron B.G. . ▸ I developed the control & monitoring system for MPPCs. ▸ That system has some functions. 
 Monitor MPPCs, measure temperature, etc.. ▸ I will solve some problem and improve the system.

13 BACKUP

switching < 1µA current leak <1Ω 25Ω resistonce on- ~1ms ~0.1ms speed of ~0W 30mW/ch 10~ 
 (HV off） consumption Power 300uW/ch ~0W (HV on） consumption Power Transistor PhotoMOS < 1µA SWITCH 14 Plan A : PhotoMOS relay HV Photo 
 MOS controller Plan B : Transistor

PHOTOMOS RELAY 15 LED ▸ Turn on/off MOSFET(switch) by LED MOSFET ▸ High insulation (>200M Ω ) ▸ Low power consumption ~10mW ( other relays ~ 1W) ▸ Normally close type → simple circuit ▸ reduce #parts used in the switch

MONITORING DARK CURRENT 16 ▸ Requirement ๏ No effect to the signal readout ๏ Large dynamic range ▸ Dark current of MPPC 
 0.5uA(initially) 
 → about 50uA(after 1.5 × 10 9 n/cm 2 irradiation) 
 4MPPCs are connected → 2~200uA ๏ Resolution (~0.01uA) ▸ to measure the I-V curve to check MPPCs

MONITORING DARK CURRENT 17 ▸ Noise from OPAMP → affect the signal readout ➡ checked the Noise Output of OPAMP 10 ns signal 1 mV noise < 100uV → No effect to the signal(~100mV)

MONITORING DARK CURRENT 18 ▸ Calibration(previous version) DC MY A PC POWER SYSTEM SUPPLY Residual = ADC -(Fit) ADC[count] Residual[ADC] 30000 10 25000 5 20000 0 15000 2 2 10000 χ χ / ndf / ndf 3.221 / 18 3.221 / 18 5 − Prob Prob 1 1 p0 p0 294.5 294.5 0.04016 0.04016 ± ± 5000 p1 p1 2.921 2.921 1.855 1.855 − − ± ± 10 − 0 0 20 40 60 80 100 0 20 40 60 80 100 Current[uA] Current[uA]

DARK CURRENT OF IRRADIATED MPPC 19 ** From Kotera-san’s slide 
 @2017July KOTO collaboration MT This value is the sum of 5 series connected MPPCs.

SIMULATION OF SWITCH 20 ‣ Use LTSpice ‣ All parts are 
 realistic one.

MONITORING HIGH VOLTAGE 21 to MPPCs HV 10M Ω Voltage 12bit follower ADC 430k Ω ▸ Bias voltage of MPPCs ~60V 
 12bit ADC → 1Count = 0.015V 
 V over =V-V br ~ 3 → 0.015V/3V =0.5% 
 → We can observe 0.5% variation in V over .

8℃ 17.1±2.4 ℃ 30.3±2.4 ℃ 30℃ 24.8±2.4 ℃ Temperature (measured by thermocouple) Temperature (measured by my system) 24℃ 8.3±2.4 ℃ 17℃ MONITORING TEMPERATURE 22 ▸ temperature sensor IC 
 This IC outputs voltage proportionally to the temperature. 
 The voltage is converted to the digital value by a 12bit ADC. This IC can measure the temperature precisely.