The UFFO (Ultra-Fast Flash Observatory) is a GRB detector on board the Lomonosov
          satellite, to be launched in 2013. The GRB trigger is provided by an X-ray detector,
          called UBAT (UFFO Burst Alarm & Trigger Telescope), which detects X-rays from the GRB
          and then triggers to determine the direction of the GRB and then alerts the Slewing Mirror
          Telescope (SMT) to turn in the direction of the GRB and record the optical photon fluxes.
          This report details the calibration of the two components: the MAPMTs and the YSO crystals
          and simulations of the UBAT. The results shows that this design can observe a GRB within a
          field of view of ±35° and can trigger in a time scale as short as 0.2 – 1.0 s
          after the appearance of a GRB X-ray spike

A. Jung

A.J. Castro-Tirado

A.S. Krasnov

B. Grossan

C. Budtz-Jørgensen

C. Eyles

C.-Y. Lin

C.R. Chen

E.V. Linder

G.-W. Na

G.F. Smoot

H. Lim

H.S. Choi

I. Yashin

I.H. Park

J. Gorosabel

J. Lee

J. Řípa

J.-E. Kim

J.-E. Suh

J.-W. Nam

J.J. Huang

J.M. Rodrigo

Jeong

K.W. Min

M.-B. Kim

M.-H.A. Huang

M.-Z. Wang

M.I. Panasyuk

N. Lund

N. Vedenkin

P. Barrillon

P. Chen

P. Connell

S. Ahmad

S. Brandt

S. Dagoret-Campagne

S. Jeong

S. Svertilov

S.-H. Chang

S.-W. Kim

T.-C. Liu

V. Reglero

Y.-W. Kim

Y.-Y. Chang

Y.J. Choi

Crossref

EAS Publications Series

The Calibration and Simulation of the GRB trigger detector of the Ultra Fast Flash Observatory

The UFFO (Ultra-Fast Flash Observatory) is a GRB detector on board the Lomonosov satellite, to be launched in 2013. The GRB trigger is provided by an X-ray detector, called UBAT (UFFO Burst Alarm &amp; Trigger Telescope), which detects X-rays from the GRB and then triggers to determine the direction of the GRB and then alerts the Slewing Mirror Telescope (SMT) to turn in the direction of the GRB and record the optical photon fluxes. This report details the calibration of the two components: the MAPMTs and the YSO crystals and simulations of the UBAT. The results shows that this design can observe a GRB within a field of view of ±35° and can trigger in a time scale as short as 0.2 – 1.0 s after the appearance of a GRB X-ray spike

Huang, M.-H.A.

Ahmad, S.

Barrillon, P.

Brandt, Søren

Budtz-Jørgensen, Carl

Castro-Tirado, A.J.

Chang, S.-H.

Chang, Y.-Y.

Chen, C.R.

Chen, P.

Choi, H.S.

Choi, Y.J.

Connell, P.

Dagoret-Campagne, S.

Eyles, C.

Grossan, B.

Huang, J.J.

Jeong, S.

Jung, A.

Kim, J.-E.

Kim, M.-B.

Kim, S.-W.

Kim, Y.-W.

Krasnov, A.S.

Lee, J.

Lim, H.

Lin, C.-Y.

Linder, E.V.

Liu, T.-C.

Lund, Niels

Min, K.W.

Na, G.-W.

Nam, J.-W.

Panasyuk, M.I.

Park, I.H.

Reglero, V.

Řípa, J.

Rodrigo, J.M.

Smoot, G.F.

Suh, J.-E.

Svertilov, S.

Vedenkin, N.

Wang, M.-Z.

I. Yashin, and

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 20, 2017Calibration and Simulation of the GRB trigger detector of the Ultra Fast FlashObservatoryHuang, M.-H.A.; Ahmad, S.; Barrillon, P.; Brandt, Søren; Budtz-Jørgensen, Carl; Castro-Tirado, A.J.;Chang, S.-H.; Chang, Y.-Y.; Chen, C.R.; Chen, P.; Choi, H.S.; Choi, Y.J.; Connell, P.; Dagoret-Campagne,S.; Eyles, C.; Grossan, B.; Huang, J.J.; Jeong, S.; Jung, A.; Kim, J.-E.; Kim, M.-B.; Kim, S.-W.; Kim, Y.-W.;Krasnov, A.S.; Lee, J.; Lim, H.; Lin, C.-Y.; Linder, E.V.; Liu, T.-C.; Lund, Niels; Min, K.W.; Na, G.-W.; Nam,J.-W.; Panasyuk, M.I.; Park, I.H.; Reglero, V.; ípa, J.; Rodrigo, J.M.; Smoot, G.F.; Suh, J.-E.; Svertilov, S.;Vedenkin, N.; Wang, M.-Z.; I. Yashin, andPublished in:E A S Publications SeriesLink to article, DOI:10.1051/eas/1361086Publication date:2013Link back to DTU OrbitCitation (APA):Huang, M-H. A., Ahmad, S., Barrillon, P., Brandt, S., Budtz-Jørgensen, C., Castro-Tirado, A. J., ... I. Yashin, A.(2013). Calibration and Simulation of the GRB trigger detector of the Ultra Fast Flash Observatory. E A SPublications Series, 61, 531-535. DOI: 10.1051/eas/1361086Gamma-ray Bursts: 15 Years of GRB AfterglowsA.J. Castro-Tirado, J. Gorosabel and I.H. Park (eds)EAS Publications Series, 61 (2013) 531–535www.eas.orgTHE CALIBRATION AND SIMULATION OF THE GRBTRIGGER DETECTOR OF THE ULTRA FAST FLASHOBSERVATORYM.-H.A. Huang1, S. Ahmad2, P. Barrillon2, S. Brandt3,C. Budtz-Jørgensen3, A.J. Castro-Tirado4, S.-H. Chang5, Y.-Y. Chang6,C.R. Chen5, P. Chen6, H.S. Choi7, Y.J. Choi8, P. Connell9,S. Dagoret-Campagne2, C. Eyles9, B. Grossan10, J.J. Huang6,S. Jeong11, A. Jung11, J.-E. Kim11, M.-B. Kim12, S.-W. Kim13,Y.-W. Kim12, A.S. Krasnov14, J. Lee12, H. Lim12, C.-Y. Lin5,E.V. Linder10, T.-C. Liu6, N. Lund3, K.W. Min8, G.-W. Na11,J.-W. Nam6, M.I. Panasyuk14, I.H. Park12, V. Reglero9, J. Rˇı´pa12,J.M. Rodrigo9, G.F. Smoot10, J.-E. Suh11, S. Svertilov14, N. Vedenkin14,M.-Z. Wang6 and I. Yashin141 Department of Energy Engineering, National United University, Miao-Li, Taiwan;e-mail: mahuang@nuu.edu.tw2 Laboratoire de l’Acce´le´rateur Line´aire, University of Paris-Sud 11, Orsay, France3 Technical University of Denmark, Copenhagen, Denmark4 Instituto de Astrofisica de Andaluc´ıa, CSIC, Granada, Spain5 National Space Organization, Taiwan6 LeCosPA, National Taiwan University, Taipei, Taiwan7 Korea Institute of Industrial Technology, Cheonan, Korea8 Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon,Korea9 University of Valencia, Valencia, Spain10 Institute for the Early Universe, Ewha Womans University, Seoul, Korea11 Department of Physics, Ewha Womans University, Seoul, Korea12 Sungkyunkwan University, Suwon, South Korea13 Department of Astronomy, Yonsei University, Seoul, Korea14 SINP, Moscow State University, Moscow, Russiac© EAS, EDP Sciences 2013DOI: 10.1051/eas/1361086Article published by EDP Sciences532 Gamma-ray Bursts: 15 Years of GRB AfterglowsAbstract. The UFFO (Ultra-Fast Flash Observatory) is a GRB detec-tor on board the Lomonosov satellite, to be launched in 2013. The GRBtrigger is provided by an X-ray detector, called UBAT (UFFO BurstAlarm & Trigger Telescope), which detects X-rays from the GRB andthen triggers to determine the direction of the GRB and then alertsthe Slewing Mirror Telescope (SMT) to turn in the direction of theGRB and record the optical photon fluxes. This report details the cal-ibration of the two components: the MAPMTs and the YSO crystalsand simulations of the UBAT. The results shows that this design canobserve a GRB within a field of view of ±35o and can trigger in a timescale as short as 0.2 – 1.0 s after the appearance of a GRB X-ray spike.1 IntroductionThe UFFO (Ultra-Fast Flash Observatory) is a GRB detector, designed to catchthe optical photons as early as possible. The UFFO-path ﬁnder is the ﬁrst detector,which consists of two sub-detectors: the Slewing Mirror Telescope (SMT) and theUFFO Burst Alert Telescope (UBAT) (Park et al. 2013). UBAT uses a codedmask detector to detect X-rays from a GRB (Kim et al. 2012). The triggeredpattern is used to determine the direction from which the GRB arrives and thenthe location of the GRB is sent to the SMT. SMT consists of a slewing mirrorin front of an optical telescope. By turning this mirror, the ﬁeld of view can beextended from the 17′ × 17′ of a telescope and CCD to almost 35o × 35o (Jeonget al. 2013). It takes only approximately 1 s to move the mirror to the desireddirection. The UFFO-path ﬁnder is installed on the Lomonosov satellite and isscheduled to be launched in 2013.This study ﬁrstly constructs a complete model of UBAT in a GEANT4 simu-lation package and then studies several key characteristics of the UBAT. Section 2describes UBAT geometry and the GEANT4 model. Section 3 presents the resultsfrom the calibration of the MAPMTs and the YSO crystals. Section 4 presents sim-ulation results, including the active energy range for X-rays, the potential noisesfrom charged particles and the determination of the direction of the GRB and theangular resolution.2 UBAT structure and modelThe top of UBAT is a 68×68 pixels coded mask, made from 1 mm thick Tungsten.In order to increase the mechanical strength, Kapton tapes are glued to the bothsides of the coded mask. At the base of UBAT is an 6×6 array of X-ray detectors,which consists of YSO crystals coupled with Multi-Anode Photo-Multiplier Tubes(MAPMT) and readout electronics. The YSO crystals convert incoming X-raysinto optical photons and then the MAPMTs convert the photons to photoelectronsand amplify the current to render it detectable. In order to isolate the opticalM.-H.A. Huang et al.: Calibration and Simulation of UFFO 533photons within one pixel, each YSO crystal is wrapped with a thin reﬂecting tape,except for the side facing the MAPMT.3 MAPMT and YSO crystal calibrationThe 64 channels MAPMT are custom made by Hamamatsu Photonics, with 8 ×8 pixels, 2.88 mm square, beneath a 0.8 mm thick frontal UV glass. The gainof each pixel of the MAPMT is deﬁned as the DAQs (Data AcQuisition system)reconstructed voltage reading per photoelectron (PE) emitted from the photocath-ode. The NuTel DAQ system is used (Yeh et al. 2004), which is capable of simul-taneously taking data from 512 channels, to calibrate the gain of the MAPMTs.A blue LED is used, which has the same wavelength as that has emitted by theYSO. This sends a pulsed light to test the MAPMT’s responses at diﬀerent highvoltages. The DAQ records the data by synchronizing with the LED pulse, insteadof the MAPMT signals. The signals S(x) as a function of DAQ reading x in mVare then ﬁtted by a Poisson functions, S(x) = A × µx/G × e−µ/Γ((x/G) + 1), todetermine the gain G and mean number of photo-electrons µ. Figure 1 shows atypical light pulse histogram with its ﬁtting result for one channel and the gainfor all channels.Fig. 1. The figure on the left side, shows a histogram of the data from channel 27. Thefigure on the center shows the Gain distributions of this MAPMT at 800V. Channel 27is located at coordinate index (4, 5) and surrounded by a black dash square. The figureon the right side shows the energy calibration for the YSO crystals.The scintillator is an array of 64 small YSO crystal blocks, each of size 2.65 mm×2.65 mm× 3 mm (thickness), which has the same dimensions as the MAPMT andwhich attaches to its frontal UV glass. For the calibration of the YSO crystals, avariable X-ray source is placed in front of the YSO and MAPMT assembly andthe signals from each cell are recorded. Figure 1 shows a combination of severalX-ray emission lines. The YSO photon yield is derived as 10.5 photons/keV andthe light yield is linear in the test range, from 22.1 keV to 59.5 keV.4 UBAT simulationIn order to simulate the operation of UBAT, a complete model of UBAT wasconstructed, using the GEANT4 simulation package. The coded mask, shown in534 Gamma-ray Bursts: 15 Years of GRB Afterglowspanel (a) of Figure 2, has an approximately 50% opening fraction and a crossingpattern of reinforcement rigs. The Kapton tape cuts oﬀ X-rays below approx-imately 5 keV and the Tungsten cuts oﬀ X-rays below approximately 200 keV.Between 5 keV and 200 keV, X-ray photons trigger UBAT and produce a certainpattern on 48× 48 detector pixel array, which then can be used to determine thedirection of arrival of the X-rays, using a reconstruction algorithm (Connel et al.2013). Figure 2 shows the patterns for three directions, relative to the main axisof the UBAT.Fig. 2. Panel (a) shows UBAT coded mask pattern. Red represents open cells and whiterepresents the blocked cells and the supporting rigs. The other three panels (b, c, d)show the patterns of triggered cells, from three directions. The color coding denotes thecharge of the triggered pixels.Several GRB light curves are used to study the trigger time. The mean X-raycount before the GRB is considered to be the background noise and counts abovebackground are treated as a GRB signal. Simulations were performed at one frameper second and both photons from the background and/or GRB were generatedindependently. Each 1 s frame can be stack together to form 2 s, 4 s, 8 s, 16 s, 32 simage frame continuously. The trigger rate of those frames of diﬀerent period arerecorded and then the running mean and RMS values are calculated (Kim et al.2012). If a frame has a rate greater than a predeﬁned level, then it passes the ﬁrstlevel trigger, called the rate trigger, and the pattern is then analyzed to determinethe direction of the arrival. If the arrival direction can be determined above somepredeﬁned SNR, it then passes the second level trigger, called the image trigger.This simulation accounts for all the blockage from the supporting structure andfor the stochastic nature of the background noise and the signal.Apart from the astronomical X-ray background, the charged particles from cos-mic rays and space radiation also contribute to noise. These eﬀects are studied byinjecting protons, electrons and gamma rays of various energy ranges, from 10 keVto 1 TeV. Low-energy charged particles cannot penetrate the 1 mm Tungstencoded mask, they could penetrate through the opening holes and trigger somepixels. However, electron ﬂux are almost constant within minutes and will notpass the rate trigger, even a large random ﬂuctuation may cause a rate trigger,their isotropic distribution may not pass the image trigger. Although high-energyparticles can penetrate the sidewalls, their signals are concentrated in just oneframe and their trails are mainly grouped in near-by pixels, which is inconsistentM.-H.A. Huang et al.: Calibration and Simulation of UFFO 535with the pattern of the coded mask. Therefore, it is concluded that charged parti-cles are not a major source of noise or can be excluded by identifying the particularabnormal detector pixel pattern they leave behind.Approximately 300 GRB light curves from BATSE were used in the triggersimulation. For a strong GRB, UBAT can trigger 0.5 s after the GRB starts andan additional second is required to slew the SMT. The UFFO can record opticalphotons as early as 1.5 s. The exact time depends on the signal-to-noise ratio.Once a rate trigger occurs, the image pattern is analyzed to determine the ar-rival direction of the X-ray source. The angular resolution is determined by com-paring the input direction of the X-rays to the reconstructed direction. Figure 3shows the angular error distribution in three energy ranges, assuming an isotropicdistribution of X-ray sources. The mean angular errors are within 17′ or 0.283oof the ﬁeld of view of the SMT telescope and only a few percent of events areoutside this limit, at a higher energy. The higher the photon energy, the larger isthe mean angular error. However, in a realistic GRB spectrum, there are muchless high-energy photons than low-energy photons. It is concluded that UBAT canlocalize GRB sources within the design values.Fig. 3. The distributions of the angular error for 5, 50, and 100 keV photons are shown,from left to right. The horizontal axis represents the angular error, in degree. The inputdirections are isotropically distributed.ReferencesConnell, P., Ahmad, S., Barrillon, P., et al., 2013, for the UFFO collaboration, proc.2012, Gamma Ray Burst Symposium (Marbella, Spain) (Oct. 8–12, 2012)Jeong, S., Nam, J.W., Ahn, K.B., et al., 2013, for the UFFO collaboration, Opt. Express,21, 2263Kim, J.E., Ahmad, S., Barrillon, P., et al., 2012, for the UFFO collaboration, Proc. SPIE8443, 84432R; doi:10.1117/12.926348Park, I.H., Ahmad, S., Barrillon, P., et al., 2013, for UFFO collaboration, submitted tothe New J. Phys.Yeh, P., Athar, A., La Barbera, N., et al., 2004, Mod. Phys. Lett. A., 19, 1117

Calibration and Simulation of the GRB trigger detector of the Ultra Fast Flash Observatory

EDP Sciences OAI-PMH repository (1.2.0)

The Calibration and Simulation of the GRB trigger detector of
          the Ultra Fast Flash Observatory

The UFFO (Ultra-Fast Flash Observatory) is a GRB detector on board the Lomonosov satellite, to be launched in 2013. The GRB trigger is provided by an X-ray detector, called UBAT (UFFO Burst Alarm & Trigger Telescope), which detects X-rays from the GRB and then triggers to determine the direction of the GRB and then alerts the Slewing Mirror Telescope (SMT) to turn in the direction of the GRB and record the optical photon fluxes. This report details the calibration of the two components: the MAPMTs and the YSO crystals and simulations of the UBAT. The results shows that this design can observe a GRB within a field of view of ±35° and can trigger in a time scale as short as 0.2 – 1.0 s after the appearance of a GRB X-ray spike

Huang, M.-H.A.

Ahmad, S.

Barrillon, P.

Brandt, S.

Budtz-Jørgensen, C.

Castro-Tirado, A.J.

Chang, S.-H.

Chang, Y.-Y.

Chen, C.R.

Chen, P.

Choi, H.S.

Choi, Y.J.

Connell, P.

Dagoret-Campagne, S.

Eyles, C.

Grossan, B.

Huang, J.J.

Jeong, S.

Jung, A.

Kim, J.-E.

Kim, M.-B.

Kim, S.-W.

Kim, Y.-W.

Krasnov, A.S.

Lee, J.

Lim, H.

Lin, C.-Y.

Linder, E.V.

Liu, T.-C.

Lund, N.

Min, K.W.

Na, G.-W.

Nam, J.-W.

Panasyuk, M.I.

Park, I.H.

Reglero, V.

Řípa, J.

Rodrigo, J.M.

Smoot, G.F.

Suh, J.-E.

Svertilov, S.

Wang, Michael

Vedenkin, N.

Wang, M.-Z.

Yashin, I.

University of Miami: Scholarship Miami

http://orbit.dtu.dk/ws/files/56967535/GRB_EAS_S1633476061000866a.pdf

Calibration and Simulation of the GRB trigger detector of the Ultra Fast Flash Observatory

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Online Research Database In Technology

EDP Sciences OAI-PMH repository (1.2.0)

University of Miami: Scholarship Miami