FAST実験3：新型大気蛍光望遠鏡の試験観測報告

Toshihiro Fujii, Max Malacari, Jose A. Bellido, Aygul Galimova, Pavel Horvath, Miroslav Hrabovsky, Dusan Mandat, Ariel Matalon, John N. Matthews, Libor Nozka, Xiaochen Ni, Miroslav Palatka,

Miroslav Pech, Paolo Privitera, Petr Schovanek, Stan B. Thomas, Petr Travnicek2016 2016 9 22

FAST 3

Fine pixelated camera

Low-cost and simplified/optimized FD

✦Target : > 1019.5 eV, ultra-high energy cosmic rays (UHECR) and neutral particles

✦Huge target volume ⇒ Fluorescence detector array Too expensive to cover a huge area

2

Single or few pixels and smaller optics

Fluorescence detector Array of Single-pixel Telescopes

Segmented mirror telescope Variable angles of elevation – steps.

construction is still in development

15 deg 45 deg

Joint Laboratory of Optics Olomouc – March 2014 7

3

20 km UHECRs

16

56 EeV zenith 500

1

2

3

1

3 2

Pho

tons

at d

iaph

ragm

P

hoto

ns a

t dia

phra

gm

Pho

tons

at d

iaph

ragm

Fluorescence detector Array of Single-pixel Telescopes ✦ Each telescope: 4 PMTs, 30°×30°

field of view (FoV).

✦ Reference design: 1 m2 aperture, 15°×15° FoV per PMT

✦ Each station: 12 telescopes, 48 PMTs, 30°×360° FoV.

✦ Deploy on a triangle grid with 20 km spacing, like “Surface Detector Array”.

✦ If 500 stations are installed, a ground coverage is ~ 150,000 km2.

✦ Geometry: Radio, SD, coincidence of three stations being investigated.

FAST Exposure

4

1.E+2

1.E+3

1.E+4

1.E+5

1.E+6

1.E+7

1.E+8

1990 2000 2010 2020 2030 2040

Expo

sure

s (L

=km

^2*s

r*yr

)

Year

Fly's Eye

AGASA

HiRes

Auger

JEM-EUSO nadir

TAx4

JEM-EUSO tilt

TA

✦ Conventional operation of FD under 15% duty cycle

✦ Target: >1019.5 eV

✦ Observation in moon night to achieve 25% duty cycle,

✦ Target: >1019.8 eV = Super GZK events (Hotspot/Warmspot)

✦ Ground area of 150,000 km2 with 25% duty cycle = 37,500 km2 (12×Auger, cost ~50 MUSD)

✦ 1 TAx4

Auger 12Preliminary

FAST

FAST

5

✦ EUSO-TA 1

✦

✦ 16

✦

✦ FAST

(Xmax)

EUSO-TA telescope + FAST camera

70 T. Fujii et al. / Astroparticle Physics 74 (2016) 64–72

Fig. 12. A 1018 eV shower simultaneously detected by the TA FD and the FAST prototype. In (a), the shower is shown in the TA FD event display, with the FOV of the FAST prototype

superimposed (see Fig. 11). In (b), the corresponding FADC trace recorded by the FAST PMT.

Fig. 13. Correlation between the impact parameter and energy of the 16 cosmic ray

shower candidates detected by the FAST prototype. Both shower parameters were

obtained from the TA standard reconstruction. The line indicates the maximum de-

tectable distance consistent with our limited data set.

to 1019.0 eV a maximum detectable distance of ∼15 km is obtained,which is a good indication of the validity of the concept introduced inSection 2.

Given the limited FOV of the FAST prototype, only a small portionof the shower development is actually observed and hence these low

energy showers have their Xmax located outside the FOV. Thus, a reli-able Gaisser–Hillas fit to the shower profile is not possible. However, acomparison between the measured signal and simulations provides auseful cross-check. For each shower candidate we generated a showerwith the same energy, direction and core position (as determined bythe TA FD reconstruction). The corresponding FAST signal was simu-lated taking into account the telescope optics, the atmospheric atten-uation and the PMT quantum efficiency as described in Section 4.2.Examples of simulated FAST traces are given in Fig. 14, together withthe measured traces of the corresponding candidate showers. Theamplitude and shape of the simulated pulses are in good agreementwith measurements.

6. Conclusions and outlook

We have presented a novel concept for an air shower fluorescencedetector which features just a few pixels covering a large field of view.The FAST concept may be used in the next generation of UHECR ex-periments, which will require low-cost detectors to achieve an orderof magnitude increase in aperture. Simulations indicate that UHECRshowers with energies above 1019.5 eV will be detected by FAST withhigh efficiency and with resolutions comparable to current genera-tion FDs. We have performed first tests of the FAST concept at theTelescope Array site where we installed a 200 mm PMT in the exist-ing EUSO-TA telescope optics. The FAST prototype took data during19 nights, for a total of 83 h. The detector operated under a variety of


Fig. 4. Photocathode current measured by the FAST PMT with the shutter closed

(dashed line) and opened (solid line).

Fig. 5. Stability of the photocathode current during a seven hour data taking run.

rent is in good agreement with expectations. The NSB level detectedby the TA FD (∼100 photons/deg2/m2/µ s) corresponds to a FAST cur-rent of ∼120 p.e/100 ns, estimated assuming a 7° circular FOV, a 20%PMT quantum efficiency, and an average optical efficiency of 40%. Ther.m.s. fluctuations in the NSB, σ NSB ∼11 p.e./100 ns, dictate the sensi-tivity of the FAST prototype. The evolution of Ipc during 7 h of contin-uous data taking is shown in Fig. 5. A smooth decrease as a functionof time is observed, representing the change in the NSB during oper-ation. We did not observe sudden jumps in the current, confirmingthat bright UV stars passing through the FAST FOV have a negligibleeffect.

The FAST PMT gain was monitored during data-taking with thestable light pulses provided by the YAP source. An example of a digi-tized YAP signal is given in Fig. 6. The signal is given in units of photo-electrons per 100 ns and is obtained by summing 5 consecutive timebins at the nominal 50 Hz sampling rate (see Section 3). The mea-sured variation in the YAP signal during a night is shown in Fig. 7. Theoverall change is small (∼7%) and consistent with the known tem-perature dependence of the PMT gain (∼ −1%/°C). We expected anincrease in the gain as the temperature drops during the night, sincethe housing of the FAST prototype is not temperature controlled.

4.2. Detection of distant laser shots

UV laser shots are routinely used for calibration of FD telescopesand atmospheric monitoring [35,36]. While traversing the atmo-sphere, the laser light side-scatters on air molecules and aerosol par-ticles into the FD field of view, producing signals similar to a UHECRshower. The TA site is equipped with a Central Laser Facility (CLF),

Fig. 6. FADC signal recorded for a YAP light pulse. It is used to monitor the relative gain

of the PMT.

Fig. 7. Variation of the YAP signal during a seven hour data taking run.

Fig. 8. FADC signal corresponding to a vertical PLS laser shot at a distance of 6 km. The

simulated signal is overplotted in red and normalized to fit the measured peak. (For

interpretation of the references to color in this figure legend, the reader is referred to

the web version of this article.)

located about 21 km from the Black Rock Mesa site. It consists of a355 nm UV laser which fires 300 vertical shots every 30 min duringdata taking. In addition, a Portable UV Laser System (PLS) [37] can bedeployed at different locations in the TA site. Both systems providelaser pulses of 2.2 mJ energy, approximately equivalent in intensityto a ∼1019.2 eV shower. We made extensive use of these laser facili-ties to characterize the performance of the FAST prototype.

The signal measured by FAST for a single PLS shot is shown inFig. 8, with the PLS located at a distance of 6 km. The signal is wellabove the NSB level, and individual pulses were detected with 100%efficiency. We used this data to calibrate the relative timing between


Fig. 12. A 1018 eV shower simultaneously detected by the TA FD and the FAST prototype. In (a), the shower is shown in the TA FD event display, with the FOV of the FAST prototype

superimposed (see Fig. 11). In (b), the corresponding FADC trace recorded by the FAST PMT.

Fig. 13. Correlation between the impact parameter and energy of the 16 cosmic ray

shower candidates detected by the FAST prototype. Both shower parameters were

obtained from the TA standard reconstruction. The line indicates the maximum de-

tectable distance consistent with our limited data set.

to 1019.0 eV a maximum detectable distance of ∼15 km is obtained,which is a good indication of the validity of the concept introduced inSection 2.

Given the limited FOV of the FAST prototype, only a small portionof the shower development is actually observed and hence these low

energy showers have their Xmax located outside the FOV. Thus, a reli-able Gaisser–Hillas fit to the shower profile is not possible. However, acomparison between the measured signal and simulations provides auseful cross-check. For each shower candidate we generated a showerwith the same energy, direction and core position (as determined bythe TA FD reconstruction). The corresponding FAST signal was simu-lated taking into account the telescope optics, the atmospheric atten-uation and the PMT quantum efficiency as described in Section 4.2.Examples of simulated FAST traces are given in Fig. 14, together withthe measured traces of the corresponding candidate showers. Theamplitude and shape of the simulated pulses are in good agreementwith measurements.

6. Conclusions and outlook

We have presented a novel concept for an air shower fluorescencedetector which features just a few pixels covering a large field of view.The FAST concept may be used in the next generation of UHECR ex-periments, which will require low-cost detectors to achieve an orderof magnitude increase in aperture. Simulations indicate that UHECRshowers with energies above 1019.5 eV will be detected by FAST withhigh efficiency and with resolutions comparable to current genera-tion FDs. We have performed first tests of the FAST concept at theTelescope Array site where we installed a 200 mm PMT in the exist-ing EUSO-TA telescope optics. The FAST prototype took data during19 nights, for a total of 83 h. The detector operated under a variety of

Astroparticle Physics, 74 (2016) 64-72

Vertical Laser~1019.3 eV

Cosmic Ray~1018.0 eV

FAST - progress in design and construction

UV Plexiglass Segmented primary mirror 8 inch PMT camera (2 x 2)

1m2 aperture FOV = 25°x 25°

variable tilt

Joint Laboratory of Optics Olomouc – Malargue November 2015 3

Prototype - October 2015

15°

45°

6Joint Laboratory of Optics in Olomouc, Czech Republic

Full-scale FAST Prototype

7

Full-scale FAST Prototype

/ Nuclear and Particle Physics Proceedings 00 (2016) 1–6 6

Figure 5: The typical spectral reflectance of FAST mirror form 260- 600 nm and spectral transmission of aperture filter. The red curverepresents the average reflectance and the blue dispersion of the mea-surements and the green curve represents the spectral transmission ofthe FAST filter.

Figure 6: The whole mechanical structure is covered with a shroud.It protect the mirrors and camera against the dust and aerosols andshields the stray light.

D. Mandat et al.

✦ 300 nm - 420 nm

✦

✦

Mirror

Filter

[nm]

/ [

%]

Ray-Trace Simulation

8420mm x 420 mm

Focal plane Bottom plane

Anode & dynodeSignal

DAQ SystemTAFD external trigger, 3~5 Hz

AmplifiersR979 CAENSignal×10

Camera of FAST, gain 5×104

High Voltage power supply, N1470 CAEN

Portable VME Electronics- Struck FADC 50 MHz sampling, SIS3350, 4 channels - GPS board, HYTEC GPS2092

15 MHz low pass filter

777,Phillips scientificSignal×50

×4

Department of Physics, University of Chicago 4

Readout ElectronicsOrtec 401A NIM Bin & TennElec TC-911 Power Supply4-Ch HV Programmable Power Supply (CAEN N1471H)SIS3350 500 MHz 12-bit FADC/DigitizerDual Timer (CAEN N93B)Quad Scaler & Preset Counter Timer (CAEN N145)8-Ch Variable Gain Amplifier (Phillips Mod. 777)8-Ch Low Threshold Discriminator (CAEN N417)15-Input Scaler (CAEN V260N)3-Fold Logic Unit (CAEN N405)

Tab. 2 Readout Electronics

A. Single Photoelectron Measurement

The Hamamatsu R5912-03 MOD PMTs used consistof 8 dynodes, come with a 20-pin base, and have a HVrange up to ⇡ 2600 V. Each of the PMTs is prefixedwith “ZS”, followed by the PMT number. We test theresponse of the PMT anode by obtaining a single photo-electron (SPE) spectrum measurement. We place a singleLED, sourced from the first output of the dual-channelfunction generator (FG), in front of the PMT. The LEDis pulsed at a frequency of 100 kHz; typical LED ampli-tude and width values are ⇡ 1.5 V and ⇡ 100 ns.

The anode output from the PMT is connected to theinput of the variable gain amplifier; the two resultingamplified outputs are put into the FADC input and firstchannel of the oscilloscope, respectively. The PMT anodesignal is a charge signal; the FADC converts the signal tocounts with a dynamic range of 0 to 4095 (12-bit range).

Time (2 ns)0 200 400 600 800 1000 1200 1400

/ (20

ns)

Coun

tN

2000

2500

3000

3500

4000

Time (2 ns)0 200 400 600 800 1000 1200 1400

/ (20

ns)

Coun

tN

820

830

840

850

860

870

880

890

900

Time (2 ns)0 200 400 600 800 1000 1200 1400

/ (20

ns)

Coun

tN

8700

8800

8900

9000

9100

9200

9300

9400

Time (2 ns)0 200 400 600 800 1000 1200 1400

/ (20

ns)

Coun

tN

2402

2404

2406

2408

2410

2412

2414

FIG. 6. PMT ZS0022 individual SPE event (top); SPE signalaveraged over all events (bottom).

The second channel of the FG is used for an externaltrigger. The FG trigger settings are adjusted to matchthe relevant NIM signal: the width is set to 20 µs, theamplitude to -800 mV. The pulsed LED signal and FGtrigger are synchronized coarsely using a dual timer mod-ule and more finely with the delay setting on the FG. The

trigger output is initially placed into the second channelof the oscilloscope, and the LED voltage is adjusted un-til a SPE signal is obtained. The signal is of order 100mV amplitude; when executing consecutive single-shotacquisitions on the scope, the goal is to obtain a SPEsignal every ten acquisitions. Once this is the case, thetrigger is put in the FADC for one minute of event read-out; a typical run will have about 5000 events. Eventsare averaged over to smooth out the SPE signal (Fig. 6).

PMTZS0018 PMTZS0022

Entries 19374Mean 551.7

RMS 1376 / ndf 2r 504.6 / 191

Constant 0.62± 23.57

Mean 28.4± 2916 Sigma 28.6± 1254

Integrated counts

0 2000 4000 6000 8000 10000 12000

Entri

es

20

40

60

80

100

120

140

160

180

200 Entries 19374Mean 551.7

RMS 1376 / ndf 2r 504.6 / 191

Constant 0.62± 23.57

Mean 28.4± 2916 Sigma 28.6± 1254

Entries 19374

Mean 0.1558RMS 69.01

/ ndf 2r 0 / −3Constant 1.41± 23.57

Mean 1.4± 2916 Sigma 6152.5± 1254

Integrated counts

−200 −100 0 100 200

Entri

es

0

20

40

60

80

100

120

140

160 Entries 19374

Mean 0.1558RMS 69.01

/ ndf 2r 0 / −3Constant 1.41± 23.57

Mean 1.4± 2916 Sigma 6152.5± 1254

Entries 9047Mean 1698RMS 2415

/ ndf 2r 270.1 / 143Constant 0.78± 32.02 Mean 37.3± 2989 Sigma 44.7± 1641

Integrated counts

−2000 0 2000 40006000800010000120001400016000

Entri

es

0

50

100

150

200

250

300

350 Entries 9047Mean 1698RMS 2415


Entries 9047

Mean 5.943RMS 67.14

/ ndf 2r 0 / −3Constant 1.41± 32.02

Mean 1.4± 2989 Sigma 6683.6± 1641

Integrated counts

−200 −100 0 100 200

Entri

es

0

10

20

30

40

50

60

70

80

90

Entries 9047

Mean 5.943RMS 67.14

/ ndf 2r 0 / −3Constant 1.41± 32.02

Mean 1.4± 2989 Sigma 6683.6± 1641

PMTZS0024 PMTZS0025

Entries 23504Mean 2111

RMS 2691 / ndf 2r 175.6 / 85

Constant 2.3± 184.8 Mean 30.6± 4582 Sigma 21.9± 1933

Integrated counts

0 5000 10000 15000 20000 25000

Entri

es

200

400

600

800

1000

1200

1400Entries 23504Mean 2111

RMS 2691 / ndf 2r 175.6 / 85

Constant 2.3± 184.8 Mean 30.6± 4582 Sigma 21.9± 1933

Entries 23504

Mean 0.857RMS 55.09

/ ndf 2r 0 / −3Constant 1.4± 184.8

Mean 1.4± 4582 Sigma 8350.8± 1933

Integrated counts

−200 −150 −100 −50 0 50 100 150

Entri

es

0

20

40

60

80

100

120

140

160Entries 23504

Mean 0.857RMS 55.09

/ ndf 2r 0 / −3Constant 1.4± 184.8

Mean 1.4± 4582 Sigma 8350.8± 1933

Entries 43157Mean 4210RMS 6062


Integrated counts

0 5000 10000 15000 20000 25000

Entri

es

200

400

600

800

1000

1200Entries 43157Mean 4210RMS 6062


Entries 43157

Mean −5.645RMS 84.44

/ ndf 2r 0 / −3Constant 1.4± 161.5

Mean 1.4± 9949 Sigma 12157.8± 2982

Integrated counts

−200 −100 0 100 200 300

Entri

es

0

50

100

150

200

250

300

Entries 43157

Mean −5.645RMS 84.44

/ ndf 2r 0 / −3Constant 1.4± 161.5

Mean 1.4± 9949 Sigma 12157.8± 2982

FIG. 7. Integrated count distribution of SPE signals, includ-ing pedestal (left peak) and SPE peak fitted to a Gaussianfor all PMTs.

After specifying the signal region for the averaged SPEsignal, we obtain a SPE integrated count distribution,sometimes displayed as a charge distribution. Since someevents will have no photoelectrons (i.e. no charge), weexpect a peak centered around zero, called the pedestal.We then have a SPE peak that we fit to a Gaussian toextract a mean SPE value (Fig 7). This parameter is keyfor other characterization measurements. The valley isthe range in which the tail end of the pedestal intersectsthe tail end of the SPE peak. A discriminator may beintroduced to remove the pedestal, leaving only the SPEspectrum. Fig. 8 shows logic for the SPE measurement.Characteristics like the peak-to-valley (P:V) ratio and

resolution can be obtained from the SPE spectrum. Thepeak-to-valley ratio is defined as the height of the SPEpeak over the height of the center valley position. Thelarger this value, the better SPE events are distinguished.For the examples in Fig. 7, the peak-to-valley ratios are⇡ 2.5. Pulse-amplitude resolution is defined as the ratio

PMT Calibration

10

6""

Figure 3: Diagram of experimental setup for the measurement of wavelength-dependent

detection efficiency using a deuterium lamp. The monochromator can be replaced by a mirror, shown in gray, for measurements of absolute detection efficiency using the laser source. The

number labels correspond to equipment information listed in Table 1 and referenced in the text.

(1) PMT Hamamatsu Photomultiplier Tube, Type

H7195P(R329P) (2) Detector Newport 918D-UV Photodiode Detectors (3) Powermeter Newport 2936-C Powermeter (4) Laser Newport Excelsior 375 CW Laser (5) Integrating Sphere Newport General Purpose Integrating Sphere, Model

70675 (6) Spectrum Lamp Newport Deuterium Lamp, Model 60000 (7) Lamp Power Supply Newport Deuterium Lamp Power Supply, Model

68840 (8) Monochromator Newport Cornerstone 130TM Motorized 1/8m

Monochromator, Model 74000 (9) Spectrophotometer Newport Spectrophotometer, Model 77700 (10) Calibration Lamp Newport Pencil Style HgAr Calibration Lamp, Model

6047

Table 1: Equipment List, numbers correspond to diagram in Figure 3

(used in AirFly experiment)Astroparticle Physics 42 (2013) 90–102


Wavelength [nm]200 300 400 500 600 700

Effic

ienc

y [%

]

0

5

10

15

20

25

Detection Efficiency vs. Wavelength

With UV Filter

Without UV Filter

2252V, 75mV, x50 amp

Wavelength [nm]200 300 400 500 600 700

Rat

e [H

z]

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

PMT Rate vs. WavelengthSignalBackgroundSignal (with UV)Background (with UV)

BkgdEntries 82Mean 439.5RMS 23.79

Background Rate [Hz]200 250 300 350 400 450 500 550 600 650 700

Cou

nts

0

1

2

3

4

5

6

7

8

9Bkgd

Entries 82Mean 439.5RMS 23.79

Background Rate (Without UV Filter)

Wavelength [nm]200 300 400 500 600 700

Pow

er [m

W]

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

-910×Power vs. Wavelength

With UV Filter

Without UV Filter

FIG. 14. PMT ZS0022 measurement with UV filter.

Hamamatsu data. To investigate this e↵ect, we utilize a46 mm UV filter (cuto↵ at 350 nm). We place the filterat the exit aperture of the monochromator. Fig. 14 com-pares results with and without the filter in place. Whileall light below 350 nm should be removed, there is anevident non-zero powermeter and signal rate reading be-tween 200 nm and 250 nm. There seems to be stray lightdue to either monochromator imperfections or leaks intothe box, which contributes a systematic increase to eachdetection e�ciency measurement at specific wavelengths.

IV. RESULTS, DISCUSSION, FUTURE WORK

A summary of results for the four characterization testscan be found in table 3. The statistical uncertainty ondetection e�ciency is O(0.1%). The systematic uncer-tainty has several contributions. One is the stability anduniformity of the deuterium lamp. Typical detection ef-ficiency measurements were operated remotely, and onlystarted 30-60 minutes after the lamp had been turnedon. The lamp manufacturer quotes O(0.5%) light ripplee↵ects.

The powermeter reading dominates systematic uncer-tainty, cited at 1% from factory calibration. Typicalpower reading values were within the linearity range pro-vided by the manufacturer, with a response of about0.5%. There is additional systematic uncertainty ofabout 0.5% due to the attenuation coe�cient. Finally,the measured spread of the detection e�ciency results istaken as a systematic variation. Assuming independente↵ects of systematics, adding contributions in quadraturegives a final systematic uncertainty value of 2.0%.

We report a final mean PMT detection e�ciency of:19.6%± (0.1%)stat ± (2.0%)syst. This is in strong agree-ment with the value provided by Hamamatsu (✏qe =22%), assuming a standard collection e�ciency for thesePMTs of approximately 90%.

PMT SPE P:V HV [V]* NL [%]** ✏390nm[%]ZS0018 2.7 2585 -1.1 18.3ZS0022 2.4 2252 -2.6 21.0ZS0024 2.3 2266 -1.6 19.8ZS0025 2.5 2369 -1.3 19.1PMT Mean 2.5± 0.2 2368± 133 -1.7± .6 19.6± 2.0Hamamatsu 2.5 2000 -2 19.8***Tab. 3 Summary of characterization measurements

(*HV for G = 107; **NL at IA ⇡ 60 mA; ***assuming✏c ⇡ 90% for Hamamatsu)

Moving forward, we will redesign and upgrade our ap-paratus. We will fully automate every piece of equipmentand readout electronics in order to remotely perform allmeasurements. In addition, we will establish a setup thatallows for testing multiple PMTs simultaneously.

V. CONCLUSION

We have successfully developed a system for e↵ectivelycharacterizing PMTs to high precision. We have out-lined results for measurements of single photoelectron,gain, non-linearity, and detection e�ciency of the FASTPMTs. We have been able to measure detection e�ciencyto within 2%.The calibrated PMTs in this report will be incorpo-

rated in the full-scale FAST prototype to be deployedat the Telescope Array experiment in June 2016. TheFAST project has demonstrated incredible potential andhas highlighted impressive collaboration across the cos-mic ray community. It will use fluorescence detection likenever before in order to contribute greatly to the stud-ies of cosmic ray showers and particle interactions at thehighest energies.

ACKNOWLEDGMENTS

I’d like to thank my adviser, Professor Paolo Privit-era, for all of his support over the years. It has meantthe world to me, and I am happy to have developed myresearch interests in his group. I’d also like to thank Dr.Toshihiro Fujii, one of the most helpful people I’ve metat KICP – it has been a pleasure working with him. I amgrateful to Professor Michael S. Turner for his guidanceas well.I’d like to thank the KICP students I have worked

with: Pavel Motloch, Jiaqi Jiang, Aygul Galimova, andMaria Merolle. Finally, I’d like to thank several studentsI’ve shared ideas with and learned from over the years:Hillary Child, Brandon Rayhaun, and Sam Saskin.


FIG. 12. SPE peak height distribution used to set discrimi-nator threshold value. The pedestal ends at around a heightof 350 ADC counts. Dividing this by the 4095 dynamic rangeof the FADC gives a discriminator threshold of ⇡ 85 mV.

in wavelength. A NIST calibrated photodiode providesthe absolute calibration for the incident light flux, deter-mining N� through a powermeter readout. The flux isreduced to the SPE level measurable by the PMT usingan integrating sphere of known transmission and incorpo-rating the light attenuation coe�cient of the apparatus13,↵ = (5.828± 0.018)⇥ 10�4. Eq. 5 can thus be rewritten:

✏ =Npe

N�= Npe ⇥

hc

Pt�↵(6)

where � is the wavelength, P is the powermeter read-ing, and t is the read out time for each step. Typicalpowermeter readings are pico-Watt order-of-magnitude.

As before, we perform a SPE spectrum measurement,obtaining both the pedestal and SPE peak. We introducea discriminator to the readout electronics. The PMT sig-nal goes through the amplifier and into the discriminatorinput. By increasing the discriminator threshold value,we remove the pedestal and ensure that only SPEs are re-ceived. The discriminator value is determined using thepeak height distribution of SPE events (Fig. 12), takingthe height position after the pedestal peak and dividingit by the dynamic range of the FADC.

Once the discriminator value is set, its output is placedinto a quad timer to check the rate, and then switched toa scaler to count SPEs. After the setup is complete, with

Wavelength [nm]0 100 200 300 400 500 600 700

Effic

iency

[%]

0

2

4

6

8

10

12

14

16

18

20

22

Detection Efficiency: FAST PMTsHamamatsu (Scaled)PMT ZS0025PMT ZS0024PMT ZS0022PMT ZS0018

18. HV = 2169V, Disc = 38mV, x20 Amp

22. HV = 2252V, Disc = 50mV, x20 Amp

24. HV = 2266V, Disc = 85mV, x20 Amp

25. HV = 2000V, Disc = 44mV, x20 Amp

FIG. 13. Detection e�ciency results with Hamamatsu mea-surement for comparison.

the powermeter and monochromator initialized, any re-maining lights in the lab are switched o↵. The computerin the lab is accessed remotely to begin data acquisi-tion. The DAQ program controls the monochromatorand powermeter. It obtains and averages 10,000 read-ings from the powermeter over 10 s for a given step; theerror, �P , is calculated in quadrature from Poisson statis-tics on both powermeter readings, lamp signal and back-ground. The lamp background corresponds to when thepowermeter values are read out while the monochroma-tor shutter is kept closed; the lamp signal is obtained foran open shutter. The final power value used in calcu-lating detection e�ciency is the di↵erence between these(P = Plamp,sig � Plamp,bkd). The PMT rate, R, is calcu-lated in a similar way, with open and closed shutters cor-responding to signal and background, respectively. Thedetection e�ciency is calculated using Eq. 6, and thestatistical error is given by Eq. 7, 8, 9:

�P = P ⇥

s

(�Plamp,sig

Plamp,sig)2 + (

�Plamp,bkd

Plamp,bkd)2 (7)

�R = R⇥

s

(�Rsig

Rsig)2 + (

�Rbkd

Rbkd)2 (8)

�✏,stat = ✏⇥r(�PP

)2 + (�RR

)2 + (�↵↵)2 (9)

A result for the detection e�ciency measurement of thePMTs can be found in Fig. 13. The results are plottedalongside scaled-down data provided by a Hamamatsumeasurement. Hamamatsu only incorporates quantume�ciency, not collection e�ciency. PMT detection e�-ciency peaks at ⇡ 20% close to 400 nm.From detection e�ciency results, we observe two

“bumps” near 200 nm and 350 nm. We expect the de-tection e�ciency to have a smooth peak, as shown in the

single-photo electron(SPE)

A. Matalon

11

August 7th, 2016

September 14th, 2016

Event 2253: log10(E(eV)): 18.57, Zen: 36.94◦, Azi: 121.14◦,Core(-7.717, -8.908), S800: 12.29 VEM/m2, Date: 20150511,Time: 052034.035539

Event 2254: log10(E(eV)): 18.53, Zen: 47.12◦, Azi: 135.49◦,Core(-4.004, -5.320), S800: 7.37 VEM/m2, Date: 20150511,Time: 053355.374323

Event 2255: log10(E(eV)): 18.50, Zen: 33.03◦, Azi: 136.36◦,Core(-4.088, 2.016), S800: 12.17 VEM/m2, Date: 20150511,Time: 070058.520151

Event 2256: log10(E(eV)): 19.76, Zen: 43.58◦, Azi: 73.75◦,Core(0.140, -3.986), S800: 118.27 VEM/m2, Date: 20150511,Time: 084906.017282

565

log(E(eV))18 18.2 18.4 18.6 18.8 19 19.2 19.4 19.6

Effic

ienc

y

0

0.2

0.4

0.6

0.8

1 Proton

Iron

log(E(eV))18 18.2 18.4 18.6 18.8 19 19.2 19.4 19.6

Ener

gy R

esol

utio

n [%

]

0

5

10

15

20

25

Proton

Iron

log(E(eV))18 18.2 18.4 18.6 18.8 19 19.2 19.4 19.6

]2 R

esol

utio

n [g

/cm

max

X 0

20

40

60

80

100

Proton

Iron

FAST Hybrid ✦ FAST

9/25

✦ FAST Hybrid

FAST → Energy: 10%, Xmax : 35 g/cm2 at 1019.5 eV

12

1.0 m × 1.0 m × 0.8 m(350 kg)

(TASD)

(FAST)

simulation

13

✦ Fluorescence detector Array of Single-pixel Telescopes (FAST)✦

✦ 10✦

✦ Full-scale FAST

✦

✦ 9/25✦ FAST hybrid Energy Xmax

✦ Energy: 10%, Xmax: 35 g/cm2 at 1019.5 eV

http://www.fast-project.org

Comment from James W. Cronin (1931-2016)I hope you can bring the single pixel fluorescence detector to practical application. While most of my colleagues are pleased with the results of Auger, I am disappointed we failed to find sources. Instrumentation like yours may make that possible some day.



Science

FAST実験3：新型大気蛍光望遠鏡の試験観測報告