We describe the current status of the Czech contribution to the ESA LOFT space mission, with emphasis on technical aspects. Expertise available in the Czech Republic will play a positive role in the LOFT project and related developments

Hudec, René

Petráček, Vojtěch

Šnita, Dalimil

Acta Polytechnica

English

René Hudec

Vojtěch Petráček

Dalimil Šnita

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Czech Contribution to LOFT

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Acta Polytechnica 53(1):30–32, 2013 © Czech Technical University in Prague, 2013available online at http://ctn.cvut.cz/ap/CZECH CONTRIBUTION TO LOFTRené Hudeca,b,∗, Vojtěch Petráčekc, Dalimil Šnitada Astronomical Institute, Academy of Sciences of the Czech Republic, CZ-25165 Ondřejov, Czech Republicb Czech Technical University in Prague, Faculty of Electrical Engineering, Technická 2, CZ-16627 Prague, CzechRepublicc Czech Technical University in Prague, Faculty of Nuclear Engineering, Břehová 78/7, CZ-11000 Prague, CzechRepublicd Institute of Chemical Technology, Technická 5, CZ-16628 Prague,Czech Republic∗ corresponding author: rhudec@asu.cas.czAbstract. We describe the current status of the Czech contribution to the ESA LOFT space mission,with emphasis on technical aspects. Expertise available in the Czech Republic will play a positive rolein the LOFT project and related developments.Keywords: X-rays, X-ray astronomy, X-ray satellites, LOFT.1. Introduction: The LOFTMissionLOFT, the Large Observatory For X-ray Timing, isa newly proposed space mission intended to provideanswers to fundamental questions about the motionof matter orbiting close to the event horizon of a blackhole, and the state of matter in neutron stars (Ferociet al., 2011). LOFT was recently selected by ESA asone of the four space mission concepts of the CosmicVision programme that will compete for a launchopportunity at the beginning of the 2020s. The ESALFT M class mission candidate is specifically designedto exploit the diagnostics of very rapid X-ray flux andspectral variability that directly probe the motion ofmatter down to distances very close to black holes andneutron stars, and also the physical state of ultradensematter (Feroci et al., 2011).LOFT will investigate variability from submillisec-ond QPOs to transient outbursts lasting years. TheLOFT LAD has an effective area ∼ 20 times largerthan its largest predecessor (the Proportional CounterArray on board RossiXTE) and much improved energyresolution.The LOFT WFM will discover and localise X-raytransients and impulsive events, and will monitor spec-tral state changes, triggering follow-up observationsand providing important science in its own right. Thebasic technologies for LOFT include:(1.) Large Area Silicon Drift Detectors;(2.) Capillary plate X-ray collimators (Feroci et al.,2011).The Large Area Detector (LAD) for LOFT has afully modular and redundant approach: there are 16independent detectors per Module, 21 independentModules per Detector Panel, and 6 independent De-tector Panels per LAD.The Wide Field Monitor for LOFT is based on thesame type of Si detectors as the Large Area detector,but it has finer pitch (300µm): < 60µm 1D positionresolution coarse (∼ 3mm) 2D resolution. It has 8cameras, 4 units, and rectangular FOV 180°× 90° (atzero resp., each camera/unit 90°× 90°)The Capillary-plate Collimator is an important partof the LOFT instrumentation. Lead-glass microcap-illary plates are commercially available and can becustomized. The LOFT baseline is as follows: FOV to∼ 43′ FWHM (2mm thickness, 25µm hole diameter,28µm pitch, Open Area Ratio 80%). The heritageis recently based on Microchannel Plates (MCP, e.g.Chandra satellite). For more details on LOFT and itsonboard experiments, see Feroci et al., 2011.2. Czech Participation in LOFTThe Czech Republic has been a full ESA member statefor almost 4 years. The LOFT mission is the 2nd ESAhigh-energy satellite with official Czech participation(after INTEGRAL). The following consortium is ex-pected to handle all aspects of the Czech contributionto LOFT.2.1. The Czech LOFT Team/ConsortiumThe following Czech institutes are involved in the ESALOFT mission and related studies:(1.) Czech Technical University in Prague (CTU);(2.) Astronomical Institute Academy of Sciences ofthe Czech Republic, Ondřejov (AI);(3.) Institute of Chemical Technology (IChT);(4.) Silesian University at Opava (SU).The Czech LOFT Consortium has the followingmembers: René Hudec CTU & AI, Vojtěch PetráčekCTU, Miroslav Finger MFF UK, Václav Vrba FZU AV30vol. 53 no. 1/2013 Czech Contribution to LOFTČR, Dalimil Šnita IChT, Vladimír Karas AI, VojtěchŠimon AI, and Zdeněk Stuchlík SU.The wider Czech LOFT consortium has 3 sections:scientific, technical, and industrial, and the membersare as follows.Scientific group: V. Karas, Z. Stuchlík, M. Bursa,M. Dovciak, J. Horak, V. Šimon. R. Hudec andG. Torok.Technical group: V. Petráček, D. Šnita, L. Pína,R. Hudec, M. Finger, V. Vrba and O. Gedeon.Industrial group: V. Maršíková, A. Inneman,M. Holl and P. Bareš.2.2. Goals of Czech participationThe following points indicate the anticipated goals ofCzech participation in the LOFT mission.• Contribute to Science through the LOFT mission –X-ray and BH (black hole) astrophysics• Participate in the study, design and developmentof a major onboard experiment (large area detec-tor), and contribute to Silicon drift detector design,development and tests.• Possibly participate in studying and designing alter-native glass capillary plate technology for the largearea detector• Complete the study and design of an additionalsmall Czech Lobster Eye X-ray All Sky Monitor• Ensure participation by Czech industry in various on-board experiments and satellite parts and systems,hardware and software, if the mission is selected.In this paper we focus on technical participation inthe LOFT project. Scientific aspects will be addressedin a separate forthcoming paper.2.3. Expertise available (for LOFT)Expertise in the following fields is available in theparticipating Czech institutions:• Si drift detectors (Czech Technical University);• Polycapillary glass plates (Institute of ChemicalTechnology);• Wide-Field Lobster Eye X-ray Monitors;• X-ray and BH astronomy and astrophysics (As-tronomical Institute, Silesian University at Opava,Charles University);• Space industry — hardware and software (CzechSpace Alliance, small companies and larger compa-nies);• Data analyses (ISDC participation).2.4. Polycapillary Glass PlatesPolycapillary glass plates form a significant part ofthe onboard instrumentation. Below we offer a briefdescription of a possible option based on experienceavailable in Czech institutions.• A possible alternative solution for MCP: a recentversion of our photolithographic method had glass0.2–1.6mm in thickness 100 × 100mm, holes assmall as 50 microns.• Developed by D. Šnita, Institute of Chemical Tech-nology in Prague.• Will need to be further developed if it is to be usedin the LOFT project.2.5. Silicon Drift DetectorsThe silicon drift detectors (SDD) are key instrumen-tation for LOFT. The following expertise is availablein Czech institutions.• Extended Czech participation in detectors for theALICE ground-based experiment.• Expertise available in design, development, manu-facture and tests of SDD.• CTU (Czech Technical University) in Prague, In-stitute of Physics, and ON Semiconductor CzechRepublic are the main Czech institutions involved.• SDD was invented by Czech scientist Pavel Rehak.3. SDD in Prague – the team’squalifications and resourcesIn this section, we briefly introduce the qualificationsand resources of the Czech SDD teams.3.1. Team composition (experience withSDD):The expert team is concentrated in the Center forPhysics of Ultra-relativistic Heavy Ion Collisions, con-sisting of teams from CTU in Prague and from theInstitute of Nuclear Physics of the Academy of Sci-ences of the Czech Republic. The following institutesare the main partners.Faculty of Nuclear Sciences and Physical En-gineering, Czech Technical University inPrague. This institute has experience in detectordesign, development, prototype production, detec-tor testing, experimental operation of SDD, radia-tion damage tests, detector defect simulation, cali-bration, data analysis, development of the controlsystem for SDD. WA98, and NA45-2 CERES andALICE experiments.Nuclear Physics Institute. This institute has ex-pertise in detector assembly, operation, testing, dataanalysis, NA45-2 CERES, SDD calibration and anal-ysis, and SDD laboratory tests.3.2. Laboratory infrastructurecurrently available for the SDDprogramThe following laboratory infrastructure is available tosupport SDD-related studies and developments:31R. Hudec, V. Petráček, D. Šnita Acta PolytechnicaFNSPE CTU Prague — clean room facility,probestation, AC-DC test equipment (LRC), lasercharge injection, bonding station (small, manual),dark box;NPI ASCR — clean room, probestation, test equip-ment, bonding station, irradiation facility (n-source,cyclotron);CERN — beam test (if needed).3.3. Production expertiseThe collaboration teams also have the following pro-duction expertise:• prototype production of SDD for the ALICE exper-iment – ICM Prague;• Post-prototyping contacts in the ON Semiconduc-tor: Roznov, Czech Republic (together with ourteam, the company tested double-sided technologyand later succesfully produced many of the pixeldetectors for the ATLAS detector at LHC);• selection and detector tests – participation in de-tector construction (Trieste and Torino);• design and production of the low voltage powersupply system for ALICE SDD.4. The LE (Lobster-Eye) All SkyMonitorIn addition, we plan to further exploit the modularconcept of the LE all-sky X-ray monitor (Hudec, 2011,Tichy et al., 2011), as a possible low-energy addition tothe recently considered LOFT onboard instrumenta-tion. The modular LE concept offers easy modificationfor EXIST, HXMT or other satellites. One modulecan be as small as 5×5×30 cm, ∼ 2 kg, and hence canbe considered as a supplementary onboard instrumentfor LOFT. The basic estimated parameters for anarray of 30 modules are given below:• daily limiting flux 10−12 erg/s/cm2;• one module 2×195 plates 78×11.5×0.1mm, 0.3mmspacing;• detector pixel size 150 microns;• total front area 1825 cm2;• energy range 0.1–10 keV;• FOV 180× 6 degrees (30 modules 6× 6 degrees);• angular resolution 3–4 arcmin;• total mass < 200 kg (for 30 modules).5. ConclusionsAfter ESA Athena was not selected for the ESA Lmission, LOFT is the only remaining X-ray astronomymission under consideration by ESA for the future.For the Czech teams, LOFT is (after INTEGRAL)the 2nd ESA high-energy astrophysical mission withofficial Czech participation.This paper has provided a brief review of possibleCzech participation in the LOFT mission and thecontribution that Czech institutes are able to make.The exact extent of our participation will depend onthe available funding. Despite extensive efforts, nofunding was available at the time when this paper waswritten. However, recent changes in the organizationof Czech space activities and the plan to establish aCzech National Space Agency give good hope that thesituation will improve soon, enabling more a effectiveCzech contribution to the LOFT mission.AcknowledgementsWe acknowledge the support provided by the Grant Agencyof the Czech Republic within the framework of grants102/09/0997 and 13-33324S “Lobster Eye X-Ray Monitor”.References[1] M. Feroci, L. Stella, M. van der Klis. The LargeObservatory for X-ray Timing (LOFT), ExperimentalAstronomy, 2011.[2] R. Hudec. New Types of Astronomical X-Ray Optics.Vulcano Workshop 2010 Frontier Objects in Astrophysicsand Particle Physics, Conference Proceedings, ItalianPhysical Society, Vol. 103, pp. 643–648, 2011.[3] V. Tichý, M. Barbera, A. Collura, et al. Lobster eyeoptics for nano-satellite x-ray monitor, EUV and X-RayOptics: Synergy between Laboratory and Space II.Edited by Hudec, René; Pina, Ladislav. Proceedings ofthe SPIE, Volume 8076, pp. 80760C–80760C-13 (2011)32

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