October 1 -10, 2014 JEM-EUSO Workshop - Toulouse 1

Balloon – EUSO Xenon / UV LED Flasher

Calibration

Evgeny Kuznetsov for UAH / MSFC GLS team

University of Alabama in Huntsville

October 1 -10, 2014 JEM-EUSO Workshop - Toulouse 2

• GLS flasher contains Xenon Lamp with 355nm optical filter and 365nm UV LED with 1W optical output.

• Receiving sensor is based on calibrated PMT (R8900-03) with attached BG3 filter. Integrated PMT response ( pulse area) for single photoelectrons was measured at different supply voltages from 700V to 900V. Entrance aperture was reduced by a mask with round a window - 1cm in diameter.

• For flasher calibration PMT sensor was installed in a dark room at 5.00m distance from flasher. Light source ( Xenon Lamp or UV LED ) was triggered from external pulse generator and PMT responses were recorded by LeCroy scope, which measured pulse area for 8 consecutive time frames – each 2.5ms wide, representing integration over 8 EUSO GTU time frames.

• To attenuate output of light sources - Xenon flasher was equipped with an extra 0.1% neutral density filter. For calibration of UV LED a neutral density filter of 1% was installed in front of the PMT sensor.

• Number of photoelectrons integrated by LeCroy scope in each GTU was calculated as a ratio of measured pulse area over a single photoelectron level of the PMT sensor, with a correction for attenuating ND filters.

• PMT sensor with attached BG3 filter represents PDM pixel with equivalent filter transparency and PMT quantum efficiency, that eliminates needs in photon to p.e. conversion. Calibration data is documented in photoelectrons.

Flasher Calibration Technique

October 1 -10, 2014 JEM-EUSO Workshop - Toulouse 3

Cooling jacket

5.00mXenon lamp

355nm optical filter 0.1% neutral density filter

PMT R8900-03

Dark Room

BG3 filter

1 cm diameter aperture HV Power Supply

U = -800VHV Power Supply U = 500; 600V; 800V; 1000V

LeCroy Oscilloscope

Pulse generator

Cooling jacket

5.00m

365nm UV LED

PMT R8900-03

Dark Room1 cm diameter aperture

HV Power Supply U = -800V

LED Driver

LeCroy Oscilloscope

Pulse area measurements

over 2.5ms

Xenon lamp trigger

Pulse generator

UV LED trigger

Arbitrary waveform generator

Multi-step waveform

1% neutral density filter

1p.e. = 18pV*s

1p.e. = 18pV*s

Setup for the Xenon flasher calibration

Setup for the UV LED flasher calibration

Pulse area measurements

over 2.5ms

BG3 filter

Functional Diagrams for Calibration Setups

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Images of the Xenon / UV LED Flasher and Calibrated PMT Sensor

UV LED

Xenon Lamp Holder with mounted filters

Xenon lamp box, holding 365nm UV LED and cooling jacket with Xenon lamp and mounted optical and neutral density filters

Balloon-EUSO GLS lasher consists of High Voltage power supply box and Xenon lamp box

Calibrated PMT sensor with 1cm diam. aperture

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• Xenon flasher was calibrated at 4 different Xenon lamp voltages ( 500V; 600V; 800V; 1000V) , that allows to adjust light intensity by factor ~ 3.5

• UV LED has large dynamic range. It was calibrated at 12 control voltage levels, stepping up with 2.5ms time intervals which allow to achieve projected levels at focal PDM pixel from 1.7 to 51 photoelectrons for distance between GLS and Balloon-EUSO : 115,000 feet

• Xenon and UV LED flasher calibration data is provided for each of control settings in two forms: - number of photoelectrons, integrated by PMT sensor with 1cm diameter aperture for 8 consecutive GTU time frames (2.5ms each);- projected number of photoelectrons at the Balloon-EUSO focal PDM pixel for the distance between GLS and balloon = 115,000 feet

• Scaling factor: PDM_f_pixel = Pulse_area/18pVs*(R1/R2)2*D2/D1*F*Natm/NDF

Calibration Data Representation

Single P.E. = 18pVs;

B-EUSO throughput = 30% ( lens_system) * 0.1855 (Ratio: light at

central pixel – to 1 cm2)

Neutral Density Filter (NDF): 0.1%(Xenon); 1%(UV LED)LED – to PMT distance (R1) : 5 m

PMT input aperture (area) (D1): 0.785 cm^2

GLS station – to Balloon (R2): 35052 m

EUSO aperture ( area) (D2): 10000 cm^2Throughput of EUSO Balloon to one pixel on the PDM (F) 0.056Atmospheric transmittance (Natm) 0.58

October 1 -10, 2014 JEM-EUSO Workshop - Toulouse 6

Control voltage applied to UV LED driver from arbitrary pulse generator 2.7V; 2.75V; 2.8V; 2.9V; 3.0V; 3.2V; 3.4V; 3.6V; 3.8V; 4.0V; 4.2V; 4.3V.These levels were programmed in order to achieve projected number of photoelectrons at focal PDM pixel from 1.7 to 51 photoelectrons

UV LED Control Strobe

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UV LED Calibration Characteristics

Projected number of photoelectrons at focal pixel versus control voltage. Calibration curve was measured before and after flight in Canada

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Calibration of the Xenon Flasher

Projected number of photoelectrons at focal PDM pixel at 4 high voltage settings. Integrated number of photoelectrons over 8 consecutive GTU time frames. Calibration was conducted after the flight in Canada.

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• Both Xenon flasher and UV LED flasher were tested an NSSTC after flight in Canada at the same as pre-flight measurement conditions

• UV LED flasher characteristics are unchanged within 5% precision• Xenon flasher showed ~ 30% lower light output in comparison with pre-flight

calibration. This was caused by degradation of the optical filter transparency.• As the Xenon flasher was not operated after flight in Canada - it was calibrated

again at NSSTC and this calibration data is documented ( as 100% light output)• In order to correct data for Xenon flasher output during flight – 355nm optical

filter was characterized and further exposed to flashes of Xenon lamp to build degradation curve versus Xenon lamp exposure.

• Correction of the in-flight Xenon flasher light output data must be done using in-flight Xenon flasher execution schedule ( Number of flashes at 1000V; duration) and extrapolated slope of the optical filter degradation curve ( to be extrapolated into negative number of flashes – that corresponds to in-flight operations)

• Xenon flasher operation table during flight ( to be checked / corrected) was created, using comments from Johannes Eser and temperature log data (temperature/humidity loggers recorded environment data in both HV Power Supply and in Xenon Lamp boxes during the whole campaign.

Correction of the Xenon_Flasher Calibration Datafor Optical Filter Degradation

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Start time Stop time Duration Triggering Number Total number Xenon lamp Notemin frequency, Hz of flashes flashes (cumulative) Voltage

9:27:00 AM 9:37:00 AM Heater - on/ no flashes (?)9:37:00 AM 9:47:00 AM 10 19 11400 11400 1000 V9:47:00 AM 9:51:00 AM 4 19 4560 15960 800 V9:52:00 AM 9:56:00 AM 4 19 4560 20520 600 V9:56:00 AM 10:01:00 AM 4 19 4560 25080 500V

10:05:00 AM 10:13:00 AM 8 19 9120 34200 1000 V10:13:00 AM 10:17:00 AM 4 19 4560 38760 800 V10:17:00 AM 10:21:00 AM 4 19 4560 43320 600 V10:21:00 AM 10:25:00 AM 4 19 4560 47880 500V10:32:00 AM 10:34:00 AM 2 20 2400 50280 1000 V Short run at 20 Hz10:36:00 AM 10:48:00 AM 12 19 13680 63960 1000 V10:48:00 AM 10:52:00 AM 4 19 4560 68520 800 V10:53:00 AM 10:57:00 AM 4 19 4560 73080 600 V10:57:00 AM 11:06:00 AM 9 19 10260 83340 500V11:06:00 AM 11:31:00 AM 25 19 28500 111840 1000 V11:33:00 AM 11:50:00 AM 17 19 19380 131220 1000 V

Xenon Flasher Execution Schedule During Flight

Temperature log data recorded in the Xenon lamp box

Flight local time

US Central Day time

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Transparency scan of 355nm optical filter

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

330 340 350 360 370 380 390

Wevelength, nm

Tran

spar

ency

, %

Center plus2mm plus4mmplus6mm plus8mm plus10mmplus12mm plus14mm plus16mmplus18mm plus20mm

355nm optical filter transparency @355nm at different locations

20.0

22.0

24.0

26.0

28.0

30.0

32.0

34.0

0.0 5.0 10.0 15.0 20.0

Offset from centerof the filter, mm

Tran

spar

ency

, %

After Flight Optical Filter Test

355nm optical filter, used with Xenon flasher was exposed to light flashes only in central region (22mm in diameter) – outer region was covered by lamp holder. After flight transparency test showed degradationof transparency of exposed area by 32% in comparison with transparency of non-exposed filter area.

Exposed filter area

Non-exposed area

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355nm Optical Filter Degradation TestAfter Flight Optical Filter Exercise Schedule:

Run# 1 2 3 4 5 TRIG Frequency, Hz: 20.0 20.0 20.0 20.0 20.0

Duration, sec: 600.0 600.0 600.0 1200.0 1200.0 Nr of flashes: 12000.0 12000.0 12000.0 24000.0 24000.0

Start Temp., C: 26.0 27.0 27.0 27.0 29.0 End Temp, C: 37.0 37.0 37.0 44.0 46.0

Extra Nr. of flashes ( at 5 Hz) : 2000.0 2000.0 1000.0 2000.0 2000.0 Total Nr of flashes: 14000.0 14000.0 13000.0 26000.0 26000.0

Total Nr of flashes cummulative: 0.0 14000.0 28000.0 41000.0 67000.0 93000.0

Light output degradation (Integral: GTU2+ GTU3+GTU4) 100.00% 98.28% 96.89% 95.19% 90.02% 87.20%

Note: After each exercise run Xenon lamp was cooled down before taking of light output measurements Uhv of the Xenon lamp = 1000V for all runs

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UV LED and Xenon Flasher Calibration data (for Xenon Flasher: End-of-Flight conditions)

)* - Calibrated PMT: R8900-03 ( QE = ~ 24% at 355nm) with 1cm diameter entrance aperture with BG-3 filter, attached via optical grease. For PDM focal pixel scaling factor: see page 5. - Number of photoelectrons at calibrated PMT sensor is calculated as a ratio of PMT response pulse integral (over 2.5ms) to single photoelectron weight with correction for neutral density filters ( For a case when ND filter is not installed)

UV LED FlasherControl Voltage, V 2.7 2.75 2.8 2.9 3 3.2 3.4 3.6 3.8 4 4.2 4.3

Projected Nr. of p.e. at PDM focal pixel 1.70 2.65 3.77 6.26 8.97 14.82 20.91 27.36 34.38 40.83 47.94 51.08

Nr. of p.e. at calibrated PMT at 5.00 m distance )* 202,222 314,444 448,333 743,333 1,065,556 1,760,000 2,483,333 3,250,000 4,083,333 4,850,000 5,694,444 6,066,667

Xenon Projected Nr. of photoelectrons at PDM Number of photoelectrons at calibrated PMT )*

Flasher focal pixel at 5.00m distance

Xenon Lamp Uhv [V]

time frame 1000V 800V 600V 500V 1000V 800V 600V 500V

GTU1 0…2.5us 30.78 15.06 6.50 3.70 3,655,556 1,788,889 772,222 438,889

GTU2 2.5us …5.0us 88.12 49.53 24.84 13.47 10,466,667 5,883,333 2,950,000 1,600,000

GTU3 5.0us …7.5us 135.27 88.82 50.14 31.76 16,066,667 10,550,000 5,955,556 3,772,222

GTU4 7.5us …10us 92.38 72.22 49.16 39.29 10,972,222 8,577,778 5,838,889 4,666,667

GTU5 10us …12.5us 53.32 44.01 31.38 25.87 6,333,333 5,227,778 3,727,778 3,072,222

GTU6 12.5us …15us 31.57 24.79 18.01 15.48 3,750,000 2,944,444 2,138,889 1,838,889

GTU7 15us …17.5us 20.35 15.43 10.66 9.03 2,416,667 1,833,333 1,266,667 1,072,222

GTU8 17.5us …20.0us 14.08 10.66 7.16 5.85 1,672,222 1,266,667 850,000 694,444

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Miscellaneous

BG 3 Optical filter transparency vs wavelength.Data from SHOTT Germany

Hamamatsu PMT R8900-03 spectral characteristics.

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LED angular characteristics

Xenon lamp L6604 spectrum

Since the balloon is at an altitude between 30.5 and 36.6 km. the transmission to the balloon is the same as it will be to JEM-EUSO. When the helicopter is at 10,000 ft (3.05 km), the transmission will be ~58% according to the chart above which comes from the 2010 purple book.