Presentation on theme: "Crab Days Roma 16- 17 October 2008 1 PolarixTeam X-Ray Polarimetry Programs in Italy Enrico Costa IASF-INAF Roma."— Presentation transcript:
Crab Days Roma 16- 17 October 2008 1 PolarixTeam X-Ray Polarimetry Programs in Italy Enrico Costa IASF-INAF Roma
Crab Days Roma 16- 17 October 2008 2 PolarixTeam POLARIX A pathfinder Mission of X-Ray Polarimetry Roma 17/10/2008 Enrico Costa, IASF – Roma, INAF, et al. On behalf of the POLARIX Team
Crab Days Roma 16- 17 October 2008 3 PolarixTeam Program of ASI for Small Missions Announcement of Opportunity with deadline October 2007 On Feb 7 2008 ASI approved phase A studies for 5 Missions Phase A studies started on April and will be completed by December 10. Each Study was supported with 750 k grant On the basis of outcome of phase A studies ASI will select two missions to be launched on 2012 and 2014. The total cost of each mission should stay wthin 50 M + launch with a VEGA 5 phase A studies approved: SAGACE, POLARIX, FLORAD, MAGIA, ADAHELI
Crab Days Roma 16- 17 October 2008 4 PolarixTeam MISSIONS in A phase SAGACE (Spectroscopic Active Galaxies And Clusters Explorer), PI: Prof. Paolo De Bernardis, Universita La Sapienza (Roma) Specroscopy study of SZ effect. Large scale structures. Hubble Constant, DM, DE. MW catalogue of Star FLORAD (Costellazione FLOreale micro-satellitare di RADiometri in banda millimetrica per l'Osservazione della Terra e dello Spazio a scala regionale) PI: Prof. Frank Marzano, Università La Sapienza (Roma) To launch a constellation of micro-satellites, each equiped with a MW radiometer in mm band, for remote sensing oftemperature, vapours, cloud water, for nowcasting and forecasting on the Mediterranean area for environment and civil protection purposes. MAGIA (Missione Altimetrica Gravimetrica geochimica lunAre) PI: Prof. A. Coradini INAF-IFSI Geochemistry and mineralogy of the moon surface by remote sensing ADAHELI (ADvanced Astronomy for HELIophysics) PI: Prof. Francesco Berrilli, Universita di Tor Vergata Photospheric and Chromospheric Dynamics studied by NIR observations. Radiance in mm band with < arcmin resolution. POLARIX (POLARimetro X) PI: Prof. Enrico COSTA, IASF Prime Contractor: IASF - Roma
Crab Days Roma 16- 17 October 2008 5 PolarixTeam POLARIX Team Enrico Costa a, Ronaldo Bellazzini c, Gianpiero Tagliaferri d, Luca Baldini c, Stefano Basso d, Johan Bregeon c, Alessandro Brez c, Oberto Citterio d, Vincenzo Cotroneo d, Sergio Di Cosimo a, Sergio Fabiani a, Marco Feroci a, Massimo Frutti a, Francesco Lazzarotto a, Giorgio Matt e, Massimo Minuti c, E.Morelli f, Fabio Muleri a,b, Giovanni Pareschi d, Michele Pinchera c, Alda Rubini a, Carmelo Sgro c, Paolo Soffitta a, Gloria Spandre c (a)Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, Roma, Italy; (b)Universita di Roma Tor Vergata, Dipartimento di Fisica, Roma, Italy; (c)Istituto Nazionale di Fisica Nucleare, Pisa, Italy; (d)Osservatorio Astronomico di Brera, INAF, Merate (Lc), Italy; (e)Universita di Roma Tre, Dipartimento di Fisica, Roma, Italy; (f)Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, Bologna (BO), Italy.
Crab Days Roma 16- 17 October 2008 6 PolarixTeam MANAGEMENT The POLARIX project will be realized, under ASI contract and general management, with a common Italian effort of following Institutes and national space firms: INAF - ISTITUTO ASTROFISICA SPAZIALE E FISICA COSMICA-ROMA INAF- OSSERVATORIO ASTRONOMICO DI BRERA INFN – SEZIONE DI PISA THALES ALENIA SPACE – TORINO THALES ALENIA SPACE – MILANO TELESPAZIO - ROMA The flight instrument and the ground systems will be developed with the responsibilities of the Institutions as listed in the table below. InstitutionResponsibility INAF-IASF-RomaCalibration, Science INAF-OA BreraTelescopes INFN – Sezione di PisaFocal Plane THAS – TorinoBUS, GS THAS – MilanoControl Electronics TELESPAZIO- Roma + ASIGround Segment INSTITUTES + ASIUser Segment
Crab Days Roma 16- 17 October 2008 7 PolarixTeam The POLARIX Concept To open the window of X-ray polarimetry by: Exploiting the capability of Gas Pixel Detectors, a new all italian technology, developed by Pisa INFN, to perform polarimetry, imaging, timing and spectroscopy of X-sources, with unprecedented sensitivity, when used as a focal plane device. Benefiting of the existing telescopes (2 FU and 1 EM) developed by OAB for the JET-X program and already tested in flight with SWIFT. The exstence of mandrels could allow (NtH) for the manufacture of two more telescopes. Benefiting of the heritage of space electronics from Thales Aleniaspace-MI and of the more recent experience of onboard handling data of complex scientific missions. Benefiting of the long heritage of Thales Aleniaspace-TO on the buildong of buses for scientific missions. Benefiting as well of commonalities with other missions under development. By a wise use of already available items we want to make a break-through mission in the tight finacial limits defined by the announcement (50M).
Crab Days Roma 16- 17 October 2008 8 PolarixTeam SPACE SEGMENT LIFETIME REQUIREMENTS DTMRCNtH Space segment lifetime1.5 years4.0 years 1.SPACE SEGMENT LIFETIME DTMRCNtH Altitude580±30 Circular(eccentricity 0.0036) Inclination 30° 5° Orbit maintenancenone OPERATIONAL ORBIT 14 months of full operation are sufficient to open the new window of X-ray polarimetry with a coverage of the major issues in the present literature. Beside a full cycle of 12 months (+ 1 SVP month) it allows for a minimal feed-back on the POLARIX results themselves. A lifetime of 4 years would allow for a adaptive program based on results of POLARIX, expected theoretical analysis and new data from other missions/observatories. Overlap with SIMBOL-X would be extremely effective.
Crab Days Roma 16- 17 October 2008 9 PolarixTeam Three modules are available (@ OAB - Merate) from Jet-X mission. Advantages: low costs Disadvantage: high mass Available Telescopes HEW meas = 15 arcsec
Crab Days Roma 16- 17 October 2008 10 PolarixTeam diam. = 30 cm thickness = 130 mm wall thickness 8.5 times less than JET-X E = 1.5 keV X-Ray test @ Panter-MPE (July 02) - E = 1.5 keV X-ray imaging test of a thin JET-X mirror shell (July 02) HEW meas = 25 arcsec
Crab Days Roma 16- 17 October 2008 11 PolarixTeam Mass: 59 kg/module Area: @ 1 keV= 150 cm2/module HEW: 15 (@1,5 keV) Telescopes Features Mass: 25 kg /module Area: @ 1 keV= 150 cm2 /module HEW: 25 (@1,5 keV)
Crab Days Roma 16- 17 October 2008 12 PolarixTeam Enrico Costa-IASF-Roma INAF Effecttsive area and Possible improvements 5 telescopi invece di tre con Coating di Carbonio Altre alternative: 6 telescopi tutti leggeri Coating Ir + C 2 detector per telescopio 5 mirrors C + Ir coating 3 mirrors Au coating (baseline)
Crab Days Roma 16- 17 October 2008 13 PolarixTeam GEM electric field pixel GEM 20 ns a E X photon (E) ASIC conversion gain collection The Gas Pixel Detector
Crab Days Roma 16- 17 October 2008 14 PolarixTeam 0.18 m CMOS VLSI 0.18 m CMOS VLSI 300 x 352 exagonal pixels, 50 m pitch300 x 352 exagonal pixels, 50 m pitch 15mmx15mm active area15mmx15mm active area Peaking time: 3-10 s, externally adjustable;Peaking time: 3-10 s, externally adjustable; Full-scale linear range: 30000 electrons; Full-scale linear range: 30000 electrons; Pixel noise: 50 electrons ENC; Pixel noise: 50 electrons ENC; Read-out mode: asynchronous or synchronous; Read-out mode: asynchronous or synchronous; Trigger mode: internal, external or self-trigger; Trigger mode: internal, external or self-trigger; Read-out clock: up to 10MHz; Read-out clock: up to 10MHz; Self-trigger threshold: 2200 electrons (10% FS); Self-trigger threshold: 2200 electrons (10% FS); Frame rate: up to 10 kHz in self-trigger mode Frame rate: up to 10 kHz in self-trigger mode (event window); (event window); Parallel analog output buffers: 1, 8 or 16; Parallel analog output buffers: 1, 8 or 16; Access to pixel content: direct (single pixel) or serial Access to pixel content: direct (single pixel) or serial (8-16 clusters, full matrix, region of interest); (8-16 clusters, full matrix, region of interest); Fill fraction (ratio of metal area to active area): 92%) Fill fraction (ratio of metal area to active area): 92%) ASIC features
Crab Days Roma 16- 17 October 2008 15 PolarixTeam mini-clusters of 4 pixels contribute to a local mini-clusters of 4 pixels contribute to a local trigger with dedicated shaping amplifier trigger with dedicated shaping amplifier threshold < 3000 e - (10% FS) threshold < 3000 e - (10% FS) individual pixel trigger mask individual pixel trigger mask independent trigger level for each 16 clusters independent trigger level for each 16 clusters event localization in rectangle containing all event localization in rectangle containing all triggered mini-clusters + user selectable triggered mini-clusters + user selectable region of 10 or 20 pixels region of 10 or 20 pixels the chip calculates the event ROI the chip calculates the event ROI (X min,Y min – X max,Y max ) for subsequent (X min,Y min – X max,Y max ) for subsequent sequential readout of selected area sequential readout of selected area Block diagram of the interface BE electronics Block diagram of the control electronics
Crab Days Roma 16- 17 October 2008 16 PolarixTeam Sealed device (only clean materials, baking & outgassing) Collaboration with Oxford Instruments Analytical Oy (Finland) GEM pitch: 50 m GEM holes diameters: 30 m, 23 m Read out pitch: 50 m Absorption gap thickness: 10 mm Collection gap thickness: 1 mm
Crab Days Roma 16- 17 October 2008 17 PolarixTeam From the laboratory to a flight prototype is A sealed Prototype. It weights 50 g + 30 g of PCB! With such a device we can perform simultaneously: Imaging (~ 150 m) Timing ( a few s) Spectroscopy (~20% @ 6 keV) + High Sensitivity Polarimetry
Crab Days Roma 16- 17 October 2008 18 PolarixTeam Tracks reconstruction The same algorithm will be implemented in thePDHU 1) The track is recorded by Xpol 2) Baricenter evaluation 3) Reconstruction of the principal axis of the track: maximization of the second moment of charge distribution 4) Reconstruction of the conversion point: major second moment (track length) + third moment along the principal axis (asymmetry of charge release) 5) Reconstruction of emission direction: pixels are weighted according to the distance from conversion point. Real track
Crab Days Roma 16- 17 October 2008 19 PolarixTeam 5.9 KeV unpolarized source 5.4 KeV polarized source Modulation factor = (Cmax – Cmin)/ (Cmax + Cmin) ˜ 50% at 5.4 KeV The angular distribution of photoelectron tracks gives polarization degree and angle Using the impact point instead than the centroid the resolution is much improved
Crab Days Roma 16- 17 October 2008 20 PolarixTeam Imaging capability Holes: 0.6 mm diameter, 2 mm apart. 55 Fe source Ne(50%)-DME(50%)
Crab Days Roma 16- 17 October 2008 21 PolarixTeam 5.4 keV polarised photons (Cr)
Crab Days Roma 16- 17 October 2008 22 PolarixTeam Modulation factor measured with two different gas mixtures: He/DME and Ne/DME @5.4 keV Cr-line energy @6.4 keV Fe energy 51.11%± 0.89% 54.26% ± 1.24%
Crab Days Roma 16- 17 October 2008 23 PolarixTeam Not only MonteCarlo 5.2 keV polarized photons for two angular rotations of the polarizer showing the good angular sensitivity. The modulation factor measured at 2.6 keV, 3.7 keV and 5.2 keV with XPOL has been compared with the Monte Carlo previsions. The agreement is very satisfying.
Crab Days Roma 16- 17 October 2008 24 PolarixTeam Environmental tests: thermal cycles and thermo-vacuum Test temperature range: between -15°C and +45°C 8 thermal cycles in a climatic chamber at atmospheric pressure with reduced humidity (<10% RH) and 1 thermo-vacuum cycle (P<10 -4 Torr) in the same temperature range. XPOL inside the climatic chamber (Angelantoni Challenge 1200) 2 thermocouples: TC_01 ( on the readout board) and TC_04 ( on top of the drift window Titanium frame ) During test a Fe 55 (Ø~ 1cm) illuminated the whole detector sensitive area TC_01 TC_04 Fe 55 source
Crab Days Roma 16- 17 October 2008 25 PolarixTeam Test point temperaturePeak amplitue (ADC counts) Relative gain 15°C reference test3200±1501 20°C higher operative temp. 2870±1500.90±0.06 10°C lower operative temp. 3583±1501.12±0.06 15°C last reference test3296±1501.03±0.06 Tests at 15°C at the beginning and at the end of the cycles (reference tests) and at +20°C and +10°C (maximum and mimimum operating temperatures) The hot and cold data taking tests show a ~-2%/°C gain dependence. Thermal cycles
Crab Days Roma 16- 17 October 2008 26 PolarixTeam Thermo-vacuum cryosta t HV feed through Chip readout feed through The thermo-vacuum chamber PT100 on window PT100 on frame Fe 55 source A vacuum vessel (Ø~250mm) is mounted around the cold head of a CRYODINE cryostat and connected to a Varian 979 leak test system that can easily reach a vacuum pressure <10 -4 Torr. The detector is mounted on the aluminum flange screwed on top of the cryostat. A series of 6 x18W resistors is glued to the lower face of this flange. The resistors heat, in competition with the cryostat freezing, allows the system to reach a large range of temperatures.
Crab Days Roma 16- 17 October 2008 27 PolarixTeam Thermo-vacuum A single +45°C, -15°C cycle at P<10-4Torr was performed Test point temperaturePeak value (ADC counts)Relative gain 15°C reference test3200±1501 20°C higher operative temp. 2900±1500.91±0.06 10°C lower operative temp.3620±1501.13±0.06 15°C last reference test3190±1500.99±0.06 T frame T window Fe 55 source image at the beginning (top) and at the end of the thermo-vacuum cycle
Crab Days Roma 16- 17 October 2008 28 PolarixTeam Analisi termiche preliminari Detector OFF Peltier (+0.1W) ASIC Temp=7.1°C Detector ON (Q=0.5W) Detector ON (Q=0.5W) Peltier (-0.4W) Peltier (-0.4W) ASIC Temp=9.4°C ASIC Temp=9.4°C
Crab Days Roma 16- 17 October 2008 29 PolarixTeam Fig. Vibration Test XPOL Board and Fixture Assembly 3D model Preliminary structural and modal FEM analyses have been performed to design the XPOL board interface frame and the vibration vertical fixture (the plate fixture was supplied with the test equipment). CAD software: UGS I-Deas NX12 FEM software: ANSYS V11 The results, see below, show that neither the equipment nor the board with the interface frame have frequency modes below 2000Hz. These results have been confirmed by the vibration tests. Modelli 3D e Analisi Mesh data: Nodes=17557 Tetrahedral Elements=6738 XPOL Board and Interface Frame Assembly - Modal Analysis, 1st Mode, 2839Hz
Crab Days Roma 16- 17 October 2008 30 PolarixTeam Sine sweep test Z axis For each axis we have performed a sine sweep between 20 and 2000Hz at 2oct/min and a random test 3dB for 75s over the predicted random vibration environment of the Pegasus rocket. In all the random tests the item was vibrated to an overall 3g rms As foreseen by the FEM analysis no resonances are present in the 20-2000Hz range. No damages have been reported X axis
Crab Days Roma 16- 17 October 2008 31 PolarixTeam Heavy Ion Medical Accelerator in Chiba (HIMAC) P < 160 MeV He C N O Ne Si Ar Fe Xe 500 MeV/n Fe beam 100-150 c/cm 2 /spill Spill = 3.3s repetition and 1.7s flat top 5 x 5 cm 2 or =5mm Gaussian shape beam At 50Hz, 1min of beam ~ 1year of exposure in space R = F cosθ dΩ dE = 6× 105 cts/s/cm 2
Crab Days Roma 16- 17 October 2008 32 PolarixTeam Filter wheel The purposes of using a filter wheel are: Preserve the experiment & measure intrinsic background Reduce the counting rate Calibrate the experiment A filter wheel is already flown on board XMM : Filter wheel on-board XMM for the EPIC experiment
Crab Days Roma 16- 17 October 2008 33 PolarixTeam To each position corresponds an operative mode: Open : Standard observation Closed : Internal Background gathering Diaphragm : Standard observation with rejection of strong sources in the field of view Beryllium filter : rate reduction at level of unprocessed data Calibration non polarized fluorescence source Calibration polarized (45 o ) Bragg diffraction
Crab Days Roma 16- 17 October 2008 34 PolarixTeam Unpolarized calibration source : (A) Fe 55 half life 2.73 yr Energy 5.89 keV (B) Cu fluorescence by Cd 109 half life 1.27 yr 8.04 keV Polarized X-ray source : Composite Bragg diffraction (45 o ) From Graphite: PVC Fluorescence (2.6 keV) from Fe 55 P = 99.9% From FLi 5.89 keV diffracted at 47.6 o P = 87.9 % Muleri et al 2007 Composite polarized source: Bragg diffraction from stacked thin Graphite and LiF permits to polarize simultaneously 2.6 keV from thin PVC sheet fluorescence by Fe 55 source and 5.89 keV by the same Fe 55 source.
Crab Days Roma 16- 17 October 2008 35 PolarixTeam POLARIX electronics is hosted in four different types of units: 3 Detector Assy electronics (FEE) 3 Back End Electronics (BEE) 1 PDHU Electronics 1Pulse Per Second Generator (PPS Gen.) (NTH) The Back End and Control Electronics
Crab Days Roma 16- 17 October 2008 36 PolarixTeam Main BEE requirements: Peak events rate up to 120 ph/(s*det) Average rate 10 ph/(s*det) Memory > 32k x 16 (in case of no global pedestal calculation) 8-bit ADC and DAC Upto 10Msample/sec ADC Serial link < 1Mbit/sec Dead time <3% w.r.t. average time between two events (i.e. ~3ms) One HV DC/DC per detector. Three voltages needed in the range 0…3kV, carried out with a voltage divider. Sinked current is very low (few nA) Analog&Digital Processing Architecture
Crab Days Roma 16- 17 October 2008 37 PolarixTeam This algorithm implies several calculation loops including: Calculation of the first, second and third moment Inverse trigonometric functions Two Change of coordinates Exponential function Square and square root calculation Floating points multiplications and divisions ON-BOARD TRACK RECONSTRUCTION - 1/2 The processor load related to the main algorithm operation loops has been evaluated for two space qualified devices: ERC-32 and DSP21020
Crab Days Roma 16- 17 October 2008 38 PolarixTeam MASS MEMORY1/2 GEMASIC CHIP For each photon collected: TO T For each hit pixel: TOT (46 pix) Time bit Energy bit RVC bitRL bitRPC bit RPH bit Coord. xCoord. Y Coord. x Coord. yCoord.Energ y 24816 88801681184 The average net telemetry data rate is: 30 ev/sec x 1184 bit/ev = 35Kbit/sec. In case of strong sources: 200 ev/sec x 1184 bit/ev = 231 kbit/sec Assuming an entire day dedicated to observe strong sources, we get: 86400 sec/day x (231 - 35) kbit/sec = 2Gbyte This mass memory can be implemented in one PDHU board using the 3D-plus technology to package SRAM memory chips.
Crab Days Roma 16- 17 October 2008 43 PolarixTeam Data rights and policy 1/2 POLARIX is a PI mission but its scientific exploitation is open to the world community. The POLARIX team will have the right to exploit exclusively data from SVP (1 month) and 25% of data from the Observing Phase. This 25% of time will be subdivided in observations organized in a Core Program, aimed to guarantee a baseline throughput of the mission. The POLARIX team will be supported in the definition of the CP and in the exploitation of data by scientists of the Italian Community. The 75% of data of Observing Phase will be assigned, following an Announcement of Opportunity issued before the launch and open to the whole community. Guest Observer Teams will be allowed to apply for any source except those included in the core program. Both Core Program an Guest Observer Programs can include Target Of Opportunity Observations. After ascertained the feasibility of the observation the proposals will be submitted to a Time Allocation Committee and selected on the basis of their scientific quality.
Crab Days Roma 16- 17 October 2008 44 PolarixTeam Data rights and policy 2/2 Assigned data will be reserved to either the Team or the Guests for one year from the delivery. After one year the data will be put in an open access archive. Guests will be supplied with a Guest Observer Handbook to prepare proposals and analyse data, with software tools, based on open source codes and documented and with all data needed for exploitation. The distributed data will be lists of qualified events including absorption point and time, energy and polarization angle, plus the data on coverage, time windows and dead time. All data will be accessible to POLARIX Team that will use them for health monitoring, calibration an to improve the software tools. The analysis of the tracks, the analysis of calibrations and the production of the response matrices of the instrument are a responsibility of the POLARIX Team. A significant fraction of the analysis software is very similar to that of SAX and SWIFT and the scientific exploitation of POLARIX, will benefit from a multifrequency approach. Therefore a significant involvement of ASDC is foreseen. The terms will be fixed by the Science Management Plan (TBD)
Crab Days Roma 16- 17 October 2008 45 PolarixTeam SCIENCE Testing General Relativity in Strong Field The plane of polarization should rotate with energy. This s an unique mark for the presence of a Black Hole. Inserire 1915+105 da articolo M. Dovˇciak, F. Muleri, R. W. Goosmann, V. Karas and G. Matt, 2008 submitted
Crab Days Roma 16- 17 October 2008 46 PolarixTeam Sensitivity
Crab Days Roma 16- 17 October 2008 47 PolarixTeam Angular Resolution: resolving the Crab
Crab Days Roma 16- 17 October 2008 48 PolarixTeam The link of Polarimetry with Hard X-ray Astronomy A certain connection does exist between physics of hard X-ray emitters and expectations of polarization. Non thermal processes, can be singled out by the presence of hard tails (e.g. in some clusters and in some shell like SNR) but also from the existence of linear polarization. The latter also provides a geometric information (e.g. the orientation of magnetic fields or the direction of particle acceleration). Alternatively the presence of hard component and the absence of polarization can provide the evidence for disordered systems (e.g. disordered magnetic fields for synchrotron, or diffuse source of seed photons in an inverse compton). Because of these overlaps and because of a reduced mismatching of observing times, a polarimeter and a hard X-ray instrument can efficiently combine, resulting in a very performing mission. This is the case of HXMT of the Chinese Space Agency
Crab Days Roma 16- 17 October 2008 49 PolarixTeam Another Option: HXMT POLARIX is not the only opportunity to fly a polarimetry pathfinder. Contacts are in progress between ASI and CNSA to harbor two telescopes with a polarimeter in the focus as piggy back devices aboard HXMT.
Crab Days Roma 16- 17 October 2008 50 PolarixTeam The Hard X-ray Modulation Telescope Mission of the Chinese Space Agency Astronomical Instr SPIE2008X-ray polarimetry with HXMT Three Major Instruments HE: Sensitive in 20-250 keV. 18 Phoswich Detectors with a F.O.V. of 5.7°×1.1° FWHM Total area 5100 cm 2. ME: Sensitive in 5-30 keV 3 Si-PIN detector arrays with a F.O.V of 5.7°×1.1°. Total collection area 952 cm 2. LE: Sensitive in 1-15 keV. Swept Charge Devices. 3 arrays each with two kinds of FOVs, 5.7°×1.1° and 5.7°×2.2°, so as to study the cosmic X-ray background in this energy band. Total collecting area of LE is 384 cm 2. Working Mode: Scan survey + pointed observation Orbit: 550 km 43° P/L: ~ 1000 kg
Crab Days Roma 16- 17 October 2008 51 PolarixTeam Astronomical Instr SPIE2008X-ray polarimetry with HXMT HXMT HXMT is a mission by the Chinese Space Agency aimed to survey the Hard X-ray Sky with Phoswich detectors, by exploitation of the direct demodulation technique. Since a fraction of the HXMT time will be spent on dedicated pointing of particular sources, and since collimated phoswich detector can anyway require long pointing and bright/medium sources (down to mCrab or fraction) it could host, with moderate additional resources a pair of X-ray telescopes, each with a photoelectric X-ray polarimeter in the focal plane. We present the design of the telescopes and the focal plane instrumentation and discuss the performance of this instrument to detect the degree and angle of linear polarization of some representative sources.
Crab Days Roma 16- 17 October 2008 52 PolarixTeam Astronomical Instr SPIE2008X-ray polarimetry with HXMT Polarimeters aboard HXMT? Since a combination of Hard X-ray measurements with polarimetry seems to be very promising, Italian and Chinese Space Agencies are negotiating the possible inclusion in the same bus of two X-ray telescopes, with in the focus two gas pixel polarimeters. The two telescopes would be located on two sides of the bus in order to minimize the design cross-talk. Requirements Total weight90 kg Maximum lenght250 cm Maximum diameter 35 cm × 2 telescopes
Crab Days Roma 16- 17 October 2008 53 PolarixTeam Astronomical Instr SPIE2008X-ray polarimetry with HXMT The telescope design guidelines The available room in the bus telescopes is sufficient to host two telescopes within the limits of 2.5 m maximum length and 35 cm maximum diameter. Since the schedule of the Mission is relatively ambitious we selected the technology of producing the telescope shells by replicating superpolished mandrels with electroforming. This technology, developed for SAX (Conti1994) and successfully applied to XMM (Gondoin1994) and JET-X (Citterio1995), whose spare unit is the optics of SWIFT X-Ray Telescope (Burrows2000), is adequately under control.
Crab Days Roma 16- 17 October 2008 54 PolarixTeam Each Telescope Astronomical Instr SPIE2008X-ray polarimetry with HXMT Shell DesignWolter 1 Shell Length30 cm × 2 Focal length2.1 m Number of shells30 Shell Thickness100 ÷ 200 μm CoatingIr + C (only 22 external) MountingSpider Weight of shells8 ÷ 16 kg Total weight41.4 ÷ 49.5 kg
Crab Days Roma 16- 17 October 2008 55 PolarixTeam The Telescope
Crab Days Roma 16- 17 October 2008 56 PolarixTeam A piggy-back solution In order to semplify AIV the two polarimeters (optics and focal plane) will be integrated within a cf tube and mounted, as piggy-back instruments, on the two sides of the HXMT bus free from solar panels.
Crab Days Roma 16- 17 October 2008 57 PolarixTeam MT Telescope Effective Area A major improvement is the use of Iridium as a reflector. The constraint of a maximum length of 2.5 meters has fixed the detector focal length to 2.1 meters. The Ir provides an improvement at higher energies. Another improvement of high impact is the addition of a thin Carbonium coating. The sensitivity of the polarimeter is maximal around 2-4 keV. In this range the M edges of Ir introduce a strong decrease of reflectivity. It has been proofed that a thin Carbonium coating significantly reduces the effect Pareschi2004).
Crab Days Roma 16- 17 October 2008 58 PolarixTeam What can we do with HXMT HXMT can detect a polarization of20% in 10 6 s Not only the amount of polarization is a relevant information. The perpendicular to the polarization plane should point the source of the reflected radiation. If SgrB2 is polarized at 70% (that means 60° < < 120° the BH should be within a cone of ± 3°. A very tight constraint to the association!
Crab Days Roma 16- 17 October 2008 59 PolarixTeam Sensitivity of polarimeter aboard HXMT
Crab Days Roma 16- 17 October 2008 60 PolarixTeam After the pathfinder POLARIX is capable to re-open the window of X-ray polarimetry to numerous sources including a few extragalactic one. Angular resolved polarimetry of PWN can be performed with a resolution < 30 A systematic sample of extragalactic sources can only be studied with a significantly larger are. This is why a polarimeter was foreseen on XEUS and is under study for IXO (see the presentation by Luigi Piro). Moreover the focal length of 20m will allow for angular resolved measurements of PWD with an angular resolution < 6. The major challenge is the development of an improved ASIC chip capable to sustain the high rate expected from bright sources.
The only polarized source already known Positive measurement: of X- ray polarization of the Crab Nebula without pulsar contamination (by lunar occultation, Weisskopf et al., 1978). P = 19.2 ± 1.0 % = 156.4 o ± 1.4 Positive measurement: of X- ray polarization of the Crab Nebula without pulsar contamination (by lunar occultation, Weisskopf et al., 1978). P = 19.2 ± 1.0 % = 156.4 o ± 1.4 o But this is only the average measurement The structure is much more complex! PSR NW jet SE jet Inner torus Outer torus With XPOL we can perform the separate polarimetry of details of the major structures f.o.v. IXO p.s.f. How turbulent is the field? How polarized is the PSR? This i s much better than any pathfinder! After 30 years we have the data from INTEGRAL. But they are also integrated in one pixel.
Rome, April 27 th - 30 th, 2009 Centro Studi Americani Via Michelangelo Caetani 32 00186 Roma http://projects.iasf-roma.inaf.it/xraypol/ The coming of age of x-ray polarimetry Scientific Organizing Committee: R. Bellazzini (Italy, co-chair), R. Blandford (U.S.A.), E. Costa (Italy, co-chair), G. Fraser (U.K.), K. Hayashida (Japan), P. Kaaret (U.S.A.), V. Karas (Czech Republic), G. Matt (Italy, co-chair), M. McConnell (U.S.A.), S. Nan Zhang (China), B. Paul (India), G. Pavlov (U.S.A.), J. Poutanen (Finland), A. Santangelo (Germany), E. Silver (U.S.A.), R. Sunayev (Germany), J. Swank (U.S.A.), G. Tagliaferri (Italy, co-chair), E. Waxman (Israel), M. Weisskopf (U.S.A.)