Czech Technical University in Prague Faculty of Electrical Engineering Department of Control Engineering EXPERIMENTAL LOBSTER EYE NANO-SATELLITE X-RAY TELESCOPE Doctoral Thesis Vladim´ır Tich´y Prague, November 2010 PhD. Programme: Electrical Engineering and Information Technology Branch of study: Control Engineering and Robotics Supervisor: Ing. Martin Hromˇc´ık, PhD. Supervisor-Specialist: Ing. Jan Jak˚ubek, PhD. Acknowledgments This thesis could not come into existence without strong support of several institutions and many people. We kindly thank all of them. First of all, I would like to thank my supervisor Ing. Martin Hromˇc´ık, PhD. for leading the work and for support. Also, I would like to thank the headmaster of Depertment of control engineering Faculty of electrical engineering of the Czech technical university, Prof. Ing. Michal Sebek,ˇ DrSc. for supply this work. I would like to thank my supervisor-specialist Ing. Jan Jak˚ubek, PhD. for help and consultations the Medipix and Timepix Detectors. Thanks him, the Institute of Experimental and Applied Physics of Czech Technical University in Prague [72] and its headmaster, Ing. Stanislav Posp´ıˇsil, DrSc. for providing the Medipix2 and Timepix detector and related equipment. Thanks to Rigaku Innovative Technologies Europe, s.r.o. [74] for provid- ing the lobster eye optics and related equipment for the laboratory tests and for manufacturing the telescope module prototypes. Thanks to the Division of Precision Mechanics and Optics of the Depart- ment of Instrumentation and Control Engineering of Faculty of Mechanical Engineering of Czech Technical University in Prague [75] for providing the laboratory and equipment for the optical tests. Thanks to Instituto Nazionale di Astrofisica-Osservatorio Astronomico di Palermo [73] , namely to Prof. Alfonso Collura, Dr. Marco Barbera and Dr. Salvatore Varisco for providing its facility for the X-ray tests and for help and consultations. I would like to thank doc. Ren´eHudec, Ing. Adolf Inneman, PhD., Ing. Jiˇr´ıMarˇs´ık, doc. Ing. Ladislav P´ına, DrSc., Ing. Veronika Semencov´aand Mgr. Libor Sv´eda,ˇ PhD. for help and consultations. This work has been carried out within the Medipix2 collaboration. The work was supported by internal grant of the Czech Technical Uni- versity in Prague No. 10-880680/13135. i X-Ray Telescope Based on Lobster Eye Optics and Pixel Detector Mgr. Vladim´ır Tich´y Czech Technical University in Prague, July 2010 Supervisor: Ing. Martin Hromˇc´ık, PhD. Supervisor-Specialist: Ing. Jan Jak˚ubek, PhD. Abstract: The dissertation analyses possibility of building experimental space X-ray telescope with the optics of the lobster-eye type. This type of optics seem to be a convenient approach for building future space all-sky X-ray monitors. Results of experiments with the lobster eye and the Medipix2 X-ray imag- ing device showing the functionality of this setup at the energy around 8keV are presented. Angular resolution and field of view were measured as well as image distortion and intensity in the dependency on the source position. Results are given. Two experimental lobster eye modules called XTM-25 and XTM-90 built in Rigaku Innovative Technologies Europe, s.r.o. are presented. Results of the tests of these modules in visible light are shown. Angular resolution of these modules is described. The lobster eye specimen called P-25 built in Rigaku Innovative Technolo- gies Europe, s.r.o. seems to be adequate to be used in a small experimental space telescope. For this reason, performance of this lobster eye was tested in a quasi-parallel beam in Instituto Nazionale di Astrofisica-Osservatorio As- tronomico di Palermo, Italy. Its key imaging parameters, i.e. field of view, angular resolution and gain were measured in several energy lines from 280eV to 8keV. At selected energy lines, measurements of gain were performed with the various incoming beam angle. Results are shown. The simulation program was developed. The key experimental results are compared to the results of this simulation program. ii Contents List of Tables vi List of Figures vii Mathematical and physical symbols x Abbreviations x Introduction 1 1 State of the art 4 1.1 Beginning of X-ray astronomy devices . 4 1.2 Related space missions with X-ray imaging instruments . ... 4 1.2.1 Einstein(HEAO-2) . 4 1.2.2 EXOSAT(HELOS).................... 5 1.2.3 ROSAT .......................... 5 1.2.4 RXTE........................... 6 1.2.5 BeppoSAX ........................ 6 1.2.6 Chandra(AXAF)..................... 7 1.2.7 XMM-Newton....................... 8 1.2.8 IXO ............................ 10 2 Goals of the dissertation 13 2.1 Medipix2 and Timepix . 13 2.2 Tests of lobster eye optics for X-ray imaging from finite distance 13 2.3 Experimentalmodules . 13 2.4 Tests of lobster eye optics for X-ray imaging from infinite dis- tance................................ 13 2.5 Simulationprogram. 14 2.6 Assesment ............................. 14 iii 3 X-ray optics overview 15 3.1 PrinciplesofX-rayoptics. 15 3.2 Pin-holesandcodedappertures . 15 3.3 RefractiveX-rayoptics . 15 3.4 ReflectiveX-rayoptics . 16 3.4.1 WolterX-rayoptics. 16 3.4.2 LobstereyeX-rayoptics . 16 3.4.3 Kirkpatrick-BaezX-rayoptics . 18 4 Lobster eye - mathematical description 23 4.1 Physical elements of X-ray reflection . 23 4.2 Imagingbylobstereye . 25 4.3 Lobstereyegeometricparameters . 26 4.4 Gain................................ 28 4.5 Fieldofview............................ 29 5 X-ray imaging devices 31 5.1 SemiconductorX-raydetectors. 32 5.1.1 Medipix2 and Timepix . 32 5.2 Microchannelplate . 36 6 Telescope module prototypes 40 6.1 Lobstereyes............................ 40 6.2 ExperimentalmoduleXTM-90. 40 6.3 ExperimentalmoduleXTM-25. 41 7 Simulation program 42 7.1 Usedprinciples .......................... 42 7.2 Simulation of one-dimensional lobster eye system . .. 43 7.2.1 Directbeams ....................... 43 7.2.2 Reflectedbeams. .. .. 45 7.3 Calculation of reflecting coefficient . 47 7.4 Functionalitytest . 47 8 Lobster eye experimental tests 48 8.1 Imagingfromfinitedistance . 48 8.1.1 Experimentalsetup . 48 8.1.2 Spatial resolution and field of view . 49 8.1.3 Image distortion and intensity . 50 8.1.4 Assesment......................... 51 8.2 Tests of telescope prototypes in visible light . .. 53 iv 8.2.1 Experimentalsetup . 53 8.2.2 Results........................... 53 8.2.3 Assesments ........................ 56 8.3 Test of lobster eye P-25 in X-ray beam XACT . 60 8.3.1 Experimentalsetup . 60 8.3.2 Centering the optics, estimation of field of view and basicimages........................ 62 8.3.3 Angularresolution . 63 8.3.4 EstimationofGain . 64 8.3.5 Gain as function of incident beam angle . 65 8.4 Assesments ............................ 65 9 Conclusions 72 10 Future work 74 11 Fulfillment of goals 75 11.1 Medipix2andTimepix . 75 11.2 Tests of lobster eye optics for X-ray imaging from finite distance 75 11.3 Experimentalmodules . 75 11.4 Tests of lobster eye optics for X-ray imaging from infinite dis- tance................................ 76 11.5 Simulationprogram. 76 11.6Assesment ............................. 76 v List of Tables 1.1 Overview of main X-ray missions with X-ray imaging instru- ments ............................... 12 6.1 Lobster eyes available for experiments . 40 8.1 Energy lines used in X-ray beam in INAF-OAPA . 60 8.2 GainofP-25atvariousenergies . 65 vi List of Figures 1.1 Artistic views of X-ray mission satellites (1) . .. 9 1.2 Artistic views of X-ray mission satellites (2) . .. 11 3.1 Wolter types of X-ray optics, source: [37] . 17 3.2 One-dimensional lobster eye principle. The rays are incom- ming from the right hand side and they are focussed to the detector on the left hand side. In reality, spaces between mir- rorsarenarrower.......................... 18 3.3 Lobster eye principle and comparsion of Schmidt and Angel lobster eyes, source: [10]. The outer sphere represents the lobster eye of the radius R. The inner sphere represents the detector. It has radius R/2 because focal length f of the lobster eye system is equal to R/2. On the top side, several rays are shown. They are focussed by outlined channels to the focus F . Around the outer sphere, Schmidt 2-D (on the left hand side), Angel (on the top side, slighly to the left) and Schmidt 1-D (on the right hand side) systems are drawn. 19 3.4 Photograph of the Schmidt type lobster eye consisting of the plates of diameter 100x80 mm, source: [42] . 20 3.5 European lobster (Homarus gammarus), source: [37] . .. 21 3.6 American lobster (Homarus americanus), source: [37] . ... 21 3.7 Principle of Kirkpatrick-Baez (KB) X-ray optics, source: [29] . 22 4.1 Icoming, reflected and transmitted beam . 24 4.2 Lobstereyegeometricparameters . 27 4.3 Effective and limiting angle. Mirrors are supposed to be ap- proximatelyparallel. 28 4.4 Lobstereyefieldofview . 29 5.1 Medipix2 device mounted on the chipboard . 33 5.2 Medipix2 pixel cell electronics [19] . 34 vii 5.3 Integral X-ray fluorescent spectra of Cd and In acquired by Medipix2[S5] ........................... 35 5.4 Differential spectra calculated from the integral spectra mea- suredbyMedipix2[S5] . 36 5.5 Absorption efficiency as the function of the photon energy ranking from 5 keV to 100 keV [23]. Typically, Medipix2 and Timepixuse300mmthickSi. 37 5.6 Timepix pixel cell electronics [20] . 38 5.7 Differential spectrum of Am241 acquired by Timepix device inTOTmode ........................... 38 5.8 Microchannelplate[35]. 39 5.9 Principle of electron multiplier [35] . 39 6.1 ModuleXTM-90onopticalbench . 41 6.2 ModuleXTM-25onopticalbench . 41 7.1 Principle of simulation of direct beams . 43 7.2 Principle of simulation of reflected beams . 45 7.3 Effectofshadingbyadjacentmirror. 46 8.1 Setupforimagingfromfinitedistance. 49 8.2 Basic images obtained by lobster eye L.U.N.D. 50 8.3 GraphofintensityfromFig.8.2(a) . 51 8.4 Image distortion. Arrows represents shifts of focal spot posi- tionfromitsidealposition .