MARGIE (Minute-of-Arc Resolution Gamma-ray Imaging Experiment) is a large area(∼104 cm2), wide field-of-view (∼1 sr), hard X-ray/gamma-ray (∼20–600 keV) coded-mask imaging telescope capable of performing a sensitive survey of both steady and transient cosmic sources. MARGIE has been selected for a NASA mission-concept study for an Ultra Long Duration (100 day) Balloon flight. We describe our program to develop the instrument based on new detector technology of either cadmium zinc telluride (CZT) semiconductors or pixellated cesium iodide (CsI) scintillators viewed by fast-timing bi-directional charge-coupled devices (CCDs). The primary scientific objectives are to image faint Gamma-Ray Bursts (GRBs) in near-real-time at the low intensity (high-redshift) end of the logN-logS distribution, thereby extending the sensitivity of present observations, and to perform a wide field survey of the Galactic plane

Altice, P P

Band, D L

Buckley, J

Cherry, M L

Guzik, T G

Hink, P L

Kappadath, S C

Macri, John R

Matteson, J L

McConnell, Mark L

O\u27Neill, Terence J

Ryan, James M.

Stacy, J G

Zych, Allen

English

UNH Scholars' Repository

University of New HampshireUniversity of New Hampshire Scholars' RepositorySpace Science Center Institute for the Study of Earth, Oceans, and Space(EOS)2000Minute-of-Arc Resolution Gamma ray ImagingExperiment—MARGIES C. KappadathLouisiana State University - Baton RougeP P. AlticeLouisiana State University - Baton RougeM L. CherryLouisiana State University - Baton RougeT G. GuzikLouisiana State University - Baton RougeJ G. StacyLouisiana State University - Baton RougeSee next page for additional authorsFollow this and additional works at: https://scholars.unh.edu/sscPart of the Astrophysics and Astronomy CommonsThis Conference Proceeding is brought to you for free and open access by the Institute for the Study of Earth, Oceans, and Space (EOS) at University ofNew Hampshire Scholars' Repository. It has been accepted for inclusion in Space Science Center by an authorized administrator of University of NewHampshire Scholars' Repository. For more information, please contact nicole.hentz@unh.edu.Recommended CitationMinute-of-Arc Resolution Gamma ray Imaging Experiment—MARGIE Kappadath, S. C. and Altice, P. P. and Cherry, M. L. andGuzik, T. G. and Stacy, J. G. and Macri, J. and McConnell, M. L. and Ryan, J. M. and Band, D. L. and Matteson, J. L. and O’Neill, T. J.and Zych, A. D. and Buckley, J. and Hink, P. L., AIP Conference Proceedings, 510, 779-783 (2000), DOI:http://dx.doi.org/10.1063/1.1303304AuthorsS C. Kappadath, P P. Altice, M L. Cherry, T G. Guzik, J G. Stacy, John R. Macri, Mark L. McConnell, James M.Ryan, D L. Band, J L. Matteson, Terence J. O'Neill, Allen Zych, J Buckley, and P L. HinkThis conference proceeding is available at University of New Hampshire Scholars' Repository: https://scholars.unh.edu/ssc/142Minute-of-Arc Resolution Gamma ray Imaging Experiment—MARGIES. C. Kappadath, P. P. Altice, M. L. Cherry, T. G. Guzik, J. G. Stacy, J. Macri, M. L. McConnell, J. M. Ryan, D. L.Band, J. L. Matteson, T. J. O’Neill, A. D. Zych, J. Buckley, and P. L. Hink  Citation: AIP Conference Proceedings 510, 779 (2000); doi: 10.1063/1.1303304 View online: http://dx.doi.org/10.1063/1.1303304 View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/510?ver=pdfcov Published by the AIP Publishing  Articles you may be interested in A search for gamma-ray burst optical emission with the automated patrol telescope AIP Conf. Proc. 428, 909 (1998); 10.1063/1.55461  Optical imaging of gamma-ray bursts with the LONEOS telescope AIP Conf. Proc. 428, 869 (1998); 10.1063/1.55459  Tracking and imaging gamma ray experiment (TIGRE) for 1 to 100 MEV gamma ray astronomy AIP Conf. Proc. 304, 701 (1994); 10.1063/1.45559  Imaging germanium telescope array for gammarays (IGETAGRAY) AIP Conf. Proc. 211, 224 (1990); 10.1063/1.39687  A gammaray imaging telescope based on liquid xenon AIP Conf. Proc. 211, 189 (1990); 10.1063/1.39682   This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to  IP:132.177.229.79 On: Mon, 24 Nov 2014 15:37:40Minute-of-Arc Resolution Gamma RayImaging Experiment - MARGIE.*S.C. Kappadath*, P.P. Altice*, M.L. Cherry*, T.G. Guzik*J.G. Stacy*-*, J. Maori*, M.L. McConnellt, J.M. Ryant, D.L. Band§>$,J.L. Matteson§, T.J. O'NeillH, A.D. ZychU, J. Buckley*, P.L. Hink#* Dept. of Physics & Astronomy, Louisiana State Univ., Baton Rouge, LA 70803t Univ. New Hampshire, Durham, NH 03824; § UC San Diego, La Jolla, CA 92093II UC Riverside, Riverside, CA 92521; # Washington Univ., St. Louts, MO 63120* Southern Univ., Baton Rouge, LA 70813; $Los Alamos Natl Lab., Los Alamos, NM 87545Abstract. MARGIE (Minute-of-Arc Resolution Gamma-ray Imaging Experiment) isa large area (~104 cm2), wide field-of-view (~1 sr), hard X-ray/gamma-ray (~20-600 keV) coded-mask imaging telescope capable of performing a sensitive survey ofboth steady and transient cosmic sources. MARGIE has been selected for a NASAmission-concept study for an Ultra Long Duration (100 day) Balloon flight. We de-scribe our program to develop the instrument based on new detector technology ofeither cadmium zinc telluride (CZT) semiconductors or pixellated cesium iodide (Csl)scintillators viewed by fast-timing bi-directional charge-coupled devices (CCDs). Theprimary scientific objectives are to image faint Gamma-Ray Bursts (GRBs) in near-real-time at the low intensity (high-redshift) end of the logN-logS distribution, therebyextending the sensitivity of present observations, and to perform a wide field survey ofthe Galactic plane.INTRODUCTIONGamma-Ray Bursts (GRBs) are intense bursts of 7 radiation, lasting from frac-tions of a second to minutes, which emit the bulk of their energy above 0.1 MeV(see e.g., Fishman and Meegan 1995; Band 1998). The origin and emission mech-anism of GRBs are still quite uncertain. It has been long recognized that the keyto unraveling the GRB mystery is the identification of burst counterparts at otherwavelengths. Over the past two years, the BeppoSAX X-ray mission has localizedover a dozen bursts to sufficiently small spatial regions (a few arc-minutes), onshort enough timescales (a few hours) so that X-ray, optical and radio telescopeshave detected the fading GRB afterglows. The recent multiwavelength observationswhich now include over four redshift measurements (Kulkarni et al. 1999) suggestthat GRBs are cosmological in origin.CP510, The Fifth Compton Symposium, edited by M. L. McConnell and J. M. Ryan© 2000 American Institute of Physics l-56396-932-7/00/$17.00779 This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to  IP:132.177.229.79 On: Mon, 24 Nov 2014 15:37:40A relativistic fireball model (see e.g., Piran 1998; Sari et al. 1998) has beenreasonably successful in explaining the observed X-ray and optical afterglows. The7~ray burst itself appears to be the result of internal shocks in the relativisticexpanding eject a and the forward shock moving through the interstellar mediumproduces the afterglows. Multiwavelength observations triggered by rapid GRBlocalization and notification provide a wealth of information about the physicalconditions in the GRB environment. The richness and complexity of the fireballphenomenon and the observational differences between GRB events require a largestatistical sample of observed bursts in order to fully unravel the physics of thesesources.The most recent report of NASA's Gamma Ray Working Group outlined a planfor the next years that included a hard X-ray (<200 keV) survey as a high priorityitem. The basis for promoting a hard X-ray instrument was that the most recentsurvey was conducted with the HEAO-1 mission, more than 20 years ago. Sincethen most of the information we have collected about the hard X-ray sky comesfrom balloon instruments on day-long flights, from occultation monitoring of strongpoint sources with BATSE on GCRO, from investigations of point sources with theOSSE instrument on CGRO, and from partial sky surveys with moderate spatialresolution (~ 13') by the SIGMA instrument on GRANAT.MARGIE (Minute-of-Arc Resolution Gamma-ray Imaging Experiment) is a largearea (~104 cm2), wide field-of-view (~1 sr), hard X-ray/7-ray (-20-600 keV)coded-mask imaging telescope capable of performing a sensitive survey of bothsteady and transient cosmic sources. MARGIE has been selected for a NASAmission-concept study for an Ultra Long Duration (100 day) Balloon flight. Theinstrument is designed to observe 30-40 GRBs in a 100 day balloon flight withsufficient S/N to permit GRB localizations to within ~2 arc-minutes. MARGIEis also ideal to conduct a hard X-ray mapping of the diffuse emission from theGalactic plane and to survey the hard X-ray sky.Centr0.5 mm thick W mask26.1° half-angle FOV1945 cm2 detector881x 883 LIRA0.5 mm pixels3.8' resolution40 60 80 100crFIGURE 1. Schematic of the MARGIE 7-ray telescope.780 This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to  IP:132.177.229.79 On: Mon, 24 Nov 2014 15:37:40MARGIE INSTRUMENT CONCEPTThe essential components of the MARGIE experiment (Cherry et al. 1999; Stacyet al. 1999; McConnell et al. 1996) are the coded aperture mask and the CsI/CCDor CZT central detector. As shown in Figure 1, the instrument consists of fiveseparate telescopes. The central telescope has an 87x87cm2 x5 mm thick tungstenmask viewed by an 1892 cm2 CsI/CCD array with (0.8 mm)2 pixels at a mask-detector separation of 150 cm. The central telescope is designed for high resolution(1.9'), narrow (8.3° half angle) field-of-view (FOV) measurements of point sourcesin addition to GRBs. The four side telescopes, each with 88 x88cm2 x0.5 mmthick masks, a 1945 cm2 detector array, 0.5 mm pixels, and 45 cm mask-detectorseparation, provide excellent sky coverage and sensitivity (26.1° half angle FOV,each with 3.8' resolution) for GRBs and point sources. Plastic scintillators coveringthe masks provide an anticoincidence veto for charged cosmic rays interactions inthe detector.The coded aperture (or "multi-pinhole") technique works by allowing an absorb-ing mask to cast a shadow pattern on a position-sensitive detection plane (e.g.,Caroli et al. 1987; Skinner et al. 1987). With a proper choice of mask patternto minimize artifacts from the imaging process, the encoded pattern can then beprocessed to reproduce an image of the sky. The mask element geometry is definedby the mask thickness and the mask element size (or width). The mask thicknessmust be sufficient to attenuate photons (hence, modulate the incident flux) in thedesired energy range. On the other hand, the thickness of the mask must be lim-ited so as to maintain uniformity of mask transmission for off-axis sources. Thetelescope angular resolution corresponds to the angular size of a mask element asseen from the detection plane, and so is dictated by the mask element size and themask-detector separation. Therefore the detector must be able to resolve the indi-vidual mask elements in the projected pattern; i.e., it must be able to locate eventswith an accuracy no larger than the mask element size. Any technology which im-proves the detector plane spatial resolution can therefore lead to an improvementin telescope angular resolution and sensitivity.DETECTOR PLANE TECHNOLOGIESThe key enabling technology for MARGIE is the central detector. In order to ob-tain the fine-grained position resolution required in the plane of the central detector,two alternate position-sensitive 7-ray detector technologies are under developmentfor use in MARGIE. The central detector will consist of five two-dimensional ar-rays of either 0.3 mm pitch cadmium zinc telluride (CZT) strip detectors or 0.5-0.9mm pitch segmented cesium iodide (Csl) scintillator. The Csl scintillators willbe viewed by a Bi-Directional Charge Coupled Device (CCD) array designed forlow-noise spectroscopy and fast timing (10 //s) applications.781 This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to  IP:132.177.229.79 On: Mon, 24 Nov 2014 15:37:40CZT DetectorsPrototype cross-strip and planar CZT detectors have been flown and flight tested.The measured background in flight is low compared to the atmospheric flux enter-ing the telescope aperture. The latest results on the overall CZT performanceand background levels at balloon altitudes are presented by Slavis et al. in theseproceedings. CZT detectors with orthogonal coplanar anode strips have also beendeveloped. Sub-millimeter position resolutions and excellent energy resolution havebeen demonstrated. These results are presented by Ryan et al. elsewhere in theseproceedings.Segmented-CsI arrays coupled to Bi-Directional CCDsSegmented Csl: CsI(Tl) is an efficient X-ray/7-ray scintillator due to its highdensity (~ 4.51 gm/cm3) and large Z. Since the light is emitted essentially isotrop-ically, the spot size diameter is comparable to the detector thickness. Therefore,one has competing requirements: a thicker detector for higher detection efficiencyand a thinner detector for better position resolution. For MARGIE, the positionresolution requirements demand a spot size <0.5 mm.Pixellated Csl arrays offer a possible solution. Large area (50x50 cm2) sub-millimeter pixel arrays up to 4 cm thick are commercially available (Krus et al.1999) in several different scintillator materials (e.g., Csl, BGO, CdWC^) and pro-duced with white paint, white epoxy or metal reflectors between the pixels. Thepixel sizes are dictated by the mechanical properties of the crystal (e.g., hardness,cleavage plane). Evaluation of these arrays is currently underway.Bi-Directional CCD: The segmented Csl scintillator output will be detectedwith a CCD. Standard CCDs are integrating devices operating at video rates (typ-ically ~30 Hz). A balloon-borne 7~ray telescope, however, demands a faster timeColumn 1 2J+1 255A A A A A__ A A AmplifiersCharge TransferDirectionRow 1Charge Cloud256Amplifier!2J+2 256FIGURE 2. Schematic view of the Bi-Directional CCD.782 This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to  IP:132.177.229.79 On: Mon, 24 Nov 2014 15:37:40resolution to veto cosmic rays hitting the detector (~10 kHz) and isolate individ-ual photons to measure their energies. We have therefore developed a Fast TimingBi-Directional CCD with 10 //s timing resolution and 50 /xm position resolution(Cherry et al. 1996).The Bi-Directional CCD employs a continuous readout scheme in which chargecollected in alternate pixel columns is clocked separately to the top and bottom ofthe CCD chip where it is amplified and read out (see Figure 2). The basic operationand performance characteristics of this device have been demonstrated with a setof prototype Bi-Directional CCDs fabricated for us at the Orbit Semiconductorsfoundry, based on a design by Suni Imaging Microsystems, Inc. (Cherry et al. 1999;Stacy et al. 1999). We are currently implementing the data readout circuitry forthe Bi-Directional CCD in a 1.2 //m CMOS ASIC design. Ultimately, both the CCDand readout electronics will be incorporated into a single monolithic CMOS chip.These further improvements will lead to an imaging device with exceptional low-noise performance and fast timing ideally suited for our astrophysical objectives.SUMMARYThe MARGIE instrument will be a large-area, wide field-of-view, hard X-ray/7-ray imaging telescope. It will be capable of providing accurate positions, and ofcharacterizing the temporal and spectral behavior of faint transient sources (e.g.,GRBs) in near-real-time, for rapid counterpart searches. It will also carry outsensitive surveys for both steady and transient cosmic sources over the course of a100-day Ultra Long Duration Balloon flight.REFERENCES1. G.J. Fishman and C.A. Meegan, Ann. Rev. Astron. Astrophys. 33, 415 (1995)2. D. Band, in 8th Marcel Grossmann Mtg. on General Relativity, ed. T. Piran, in press(astro-ph/9712193, 1998)3. S. R. Kulkarni et al., Nature, submitted (astro-ph/9902272 v2, 1999).4. T. Piran, preprint, astro-ph/9810256 (1998)5. R. Sari, T. Piran and R. Narayan, ApJ 497 L17 (1998)6. M.L. Cherry et al., Proc. SPIE 3765, in press (1999)7. J.G. Stacy et al., Proc. 19th Texas Symposium (Paris), in press (1999)8. M. McConnell et al., Proc. SPIE 2806, 349 (1996)9. E. Caroli et al., Space Sci. Rev. 45, 349 (1987)10. G.K. Skinner et al., Astrophys.Space Sci. 136, 337 (1987)11. K. Slavis et al., these proceedings12. J. Ryan et al., these proceedings13. D. Krus et al., Proc. SPIE Conf. 3768, in press (1996)14. M.L. Cherry et al., Proc. SPIE 2806, 551 (1996)783 This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to  IP:132.177.229.79 On: Mon, 24 Nov 2014 15:37:40

Minute-of-Arc Resolution Gamma ray Imaging Experiment—MARGIE

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Minute-of-Arc Resolution Gamma ray Imaging Experiment—MARGIE

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