crab days roma 16- 17 october 2008 1 polarixteam x-ray polarimetry programs in italy enrico costa...
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Crab Days Roma 16- 17 October 2008 1PolarixTeam
X-Ray Polarimetry Programs in Italy
Enrico CostaIASF-INAF Roma
Crab Days Roma 16- 17 October 2008 2PolarixTeam
POLARIX
A pathfinder Mission of X-Ray A pathfinder Mission of X-Ray PolarimetryPolarimetryRoma 17/10/2008Roma 17/10/2008
Enrico CostaEnrico Costa, , IASFIASF – Roma– Roma, INAF, et al., INAF, et al.
On behalf of the POLARIX Team
Crab Days Roma 16- 17 October 2008 3PolarixTeam
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 4PolarixTeam
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-IFSIGeochemistry 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, IASFPrime Contractor: IASF - Roma
Crab Days Roma 16- 17 October 2008 5PolarixTeam
POLARIX Team
Enrico Costaa, Ronaldo Bellazzini c, Gianpiero Tagliaferrid, Luca Baldinic, Stefano Bassod, Johan Bregeonc, Alessandro Brezc, Oberto Citteriod, Vincenzo
Cotroneod, Sergio Di Cosimoa, Sergio Fabiania, Marco Ferocia, Massimo Fruttia, Francesco Lazzarottoa, Giorgio Matte, Massimo Minutic, E.Morellif, Fabio
Muleria,b, Giovanni Pareschid, Michele Pincherac , Alda Rubinia, Carmelo Sgroc, Paolo Soffittaa, Gloria Spandrec
(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 6PolarixTeam
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.
Institution Responsibility
INAF-IASF-Roma Calibration, Science
INAF-OA Brera Telescopes
INFN – Sezione di Pisa Focal Plane
THAS – Torino BUS, GS
THAS – Milano Control Electronics
TELESPAZIO- Roma + ASI Ground Segment
INSTITUTES + ASI User Segment
Crab Days Roma 16- 17 October 2008 7PolarixTeam
The POLARIX ConceptTo 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 8PolarixTeam
SPACE SEGMENT LIFETIME REQUIREMENTS DT MRC NtH
Space segment lifetime 1.5 years 4.0 years
1.SPACE SEGMENT LIFETIME
DT MRC NtH
Altitude 580±30
Circular (eccentricity ≤ 0.0036)
Inclination ≤ 30° ≤ 5°
Orbit maintenance none none
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 9PolarixTeam
•Three modules are available (@ OAB - Merate) from Jet-X mission.
•Advantages: low costs
•Disadvantage: high mass
Available TelescopesAvailable Telescopes
HEWHEWmeasmeas = 15 arcsec = 15 arcsec
Crab Days Roma 16- 17 October 2008 10PolarixTeam
• diam. = 30 cm
• thickness = 130 mm
• wall thickness 8.5 times less than JET-X
X-Ray test @ Panter-MPE (July ’02) - E = 1.5 keVE = 1.5 keV
X-ray imaging test of a X-ray imaging test of a thin JET-X mirror shell thin JET-X mirror shell (July ‘02)(July ‘02)
HEWHEWmeasmeas = 25 arcsec = 25 arcsec
Crab Days Roma 16- 17 October 2008 11PolarixTeam
• Mass: 59 kg/module
• Area: @ 1 keV= 150 cm2/module
• HEW: 15” (@1,5 keV)
TelescopesTelescopes Features Features
• Mass: 25 kg/module
• Area: @ 1 keV= 150 cm2/module
• HEW: 25” (@1,5 keV)
Crab Days Roma 16- 17 October 2008 12PolarixTeam
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 mirrorsC + Ir coating
3 mirrorsAu coating(baseline)
Crab Days Roma 16- 17 October 2008 13PolarixTeam
GEM electric field
pixel
GEM
20 ns
a E
X photon (E)
ASIC
conversion gain
collection
2cos
The Gas Pixel Detector
Crab Days Roma 16- 17 October 2008 14PolarixTeam
• 0.180.18m CMOS VLSIm CMOS VLSI•300 x 352 exagonal pixels, 50300 x 352 exagonal pixels, 50m pitchm pitch
•15mmx15mm active area15mmx15mm active area•Peaking time: 3-10 Peaking time: 3-10 s, externally adjustable;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 modeFrame 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 featuresASIC features
Crab Days Roma 16- 17 October 2008 15PolarixTeam
mini-clusters of 4 pixels contribute to a mini-clusters of 4 pixels contribute to a locallocal trigger with dedicated shaping amplifiertrigger with dedicated shaping amplifier
threshold < 3000 ethreshold < 3000 e- - (10% FS)(10% FS)individual pixel trigger mask individual pixel trigger mask
independent trigger level for each 16 clustersindependent trigger level for each 16 clustersevent 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 pixelsregion of 10 or 20 pixels
the chip calculates the event ROIthe chip calculates the event ROI (X(Xminmin,Y,Yminmin – X – Xmaxmax,Y,Ymaxmax) for subsequent ) for subsequent
sequential readout of selected areasequential readout of selected area
Block diagram of the interface BE electronics Block diagram of the control electronics
Crab Days Roma 16- 17 October 2008 16PolarixTeam
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 17PolarixTeam
From the laboratory to a flight prototype is
A sealed Prototype. It weights 50 g + 30 g of PCB!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 18PolarixTeam
Tracks reconstructionTracks reconstructionThe same algorithm will be implemented in thePDHUThe 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 19PolarixTeam
5.9 KeV unpolarized source 5.4 KeV polarized source
Modulation factor = (Cmax – Cmin)/ (Cmax + Cmin) ˜ 50% at 5.4 KeV
AT
BS
S
nnMDP
2
1
02cos BAC
The angular distribution of photoelectron tracks gives polarization degree and angle
Using the impact point instead than the centroid the resolution is much Using the impact point instead than the centroid the resolution is much improvedimproved
Crab Days Roma 16- 17 October 2008 20PolarixTeam
Imaging capability
Holes: 0.6 mm diameter, 2 mm apart.
55Fe source Ne(50%)-DME(50%)
Crab Days Roma 16- 17 October 2008 21PolarixTeam
5.4 keV polarised photons (Cr)5.4 keV polarised photons (Cr)5.4 keV polarised photons (Cr)
Crab Days Roma 16- 17 October 2008 22PolarixTeam
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 23PolarixTeam
Not only MonteCarloNot 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 24PolarixTeam
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<10-4Torr) 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 Fe55 (Ø~ 1cm) illuminated the whole detector
sensitive area
TC_01
TC_04
Fe55 source
Crab Days Roma 16- 17 October 2008 25PolarixTeam
Test point temperature Peak amplitue (ADC counts)
Relative gain
15°C reference test 3200±150 1
20°C higher operative temp.
2870±150 0.90±0.06
10°C lower operative temp.
3583±150 1.12±0.06
15°C last reference test 3296±150 1.03±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 cyclesThermal cycles
Crab Days Roma 16- 17 October 2008 26PolarixTeam
Thermo-vacuumThermo-vacuum
cryostat
HV feed through Chip
readout feed through
The thermo-vacuum chamber
PT100 onwindow
PT100on frame
Fe55 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
<10-4Torr.
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 27PolarixTeam
Thermo-vacuumThermo-vacuum
A single +45°C, -15°C cycle at P<10-4Torr was performed
Test point temperature Peak value (ADC counts) Relative gain
15°C reference test 3200±150 1
20°C higher operative temp.
2900±150 0.91±0.06
10°C lower operative temp. 3620±150 1.13±0.06
15°C last reference test 3190±150 0.99±0.06
T frameT window
Fe55 source image at the beginning (top) and at the end of the thermo-vacuum
cycle
Crab Days Roma 16- 17 October 2008 28PolarixTeam
Analisi termiche preliminari
• Detector OFF
• Peltier (+0.1W)
• ASIC Temp=7.1°C
Detector ON Detector ON (Q=0.5W)(Q=0.5W)
Peltier (-0.4W)Peltier (-0.4W) ASIC Temp=9.4°CASIC Temp=9.4°C
Crab Days Roma 16- 17 October 2008 29PolarixTeamFig. 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 V11The 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 AnalisiModelli 3D e Analisi
Modes Frequence [Hz] 1. 2838.7 2. 3268.2 3. 3817.6 4. 3899. 5. 4090.4 6. 4296.5
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 30PolarixTeam
Sine sweep test
Z axis
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 3grms
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 31PolarixTeam
Heavy Ion Medical Accelerator in Chiba (HIMAC)
P < 160 MeVHe
CNO
NeSi
ArFe Xe
500 MeV/n Fe beam100-150 c/cm2/spillSpill = 3.3s repetition and 1.7s flat top5 x 5 cm2 or =5mm Gaussian shape beamAt 50Hz, 1min of beam ~ 1year of exposure in spaceR = ∫F cosθ dΩ dE = 6× 10−5 cts/s/cm2
Crab Days Roma 16- 17 October 2008 32PolarixTeam
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 33PolarixTeam
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 non polarized fluorescence source
Calibration polarized (45o) Bragg diffraction
Crab Days Roma 16- 17 October 2008 34PolarixTeam
Unpolarized calibration source :
(A) Fe55 half life 2.73 yr Energy 5.89 keV
(B) Cu fluorescence by Cd109 half life 1.27 yr 8.04 keV
Polarized X-ray source :
Composite
Bragg diffraction (45o)
From Graphite: PVC Fluorescence (2.6 keV) from Fe55 P = 99.9%
From FLi 5.89 keV diffracted at 47.6o 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 Fe55 source and 5.89 keV by the same Fe55 source.
Crab Days Roma 16- 17 October 2008 35PolarixTeam
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 36PolarixTeam
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 37PolarixTeam
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 38PolarixTeam
MASS MEMORY 1/2
GEM ASIC CHIP
For each photon collected: TOT
For each hit pixel:
TOT(46 pix)
Time bit
Energy bit
RVC bit RL bit RPC bit
RPH bit
Coord. x
Coord. Y
Coord. x
Coord. y
Coord.
Energy
24 8 16 16 8 8 80 16 8 1184
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.
All rights reserved © 2007, Thales Alenia Space
POLARIX
Total Mass Budget906 kg (included contigngency)
Total Power BudgetService Module: 356 WPayload: 80 WTotal: 523 W
All rights reserved © 2007, Thales Alenia Space
POLARIX
All rights reserved © 2007, Thales Alenia Space
POLARIX
MISSION ANALYSIS1/
VEGA PERFORMANCES
All rights reserved © 2007, Thales Alenia Space
POLARIX
Segmento terraL’orbita LEO equatoriale permette di effettuare la comunicazione tra segmento-volo e segmento-Terra Polar-X in Banda S utilizzando la stazione di Terra ASI a Malindi.
Come schema della rete di comunicazione, Centro di controllo missione e Centro delle operazioni scientifiche si potranno riprendere gli schemi già ampiamente collaudati nelle missioni nazionali (SAX, SWIFT, COSMO)
Lo studio della architettura della stazione di terra sarà svolto da Telespazio, coinvolta nello studio con contratto di consulenza.
Crab Days Roma 16- 17 October 2008 43PolarixTeam
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 44PolarixTeam
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 45PolarixTeam
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 46PolarixTeam
Sensitivity
Crab Days Roma 16- 17 October 2008 47PolarixTeam
Angular Resolution: resolving the Crab
Crab Days Roma 16- 17 October 2008 48PolarixTeam
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 49PolarixTeam
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 50PolarixTeam
The Hard X-ray Modulation Telescope Missionof the Chinese Space Agency
Astronomical Instr SPIE2008 X-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 cm2. • 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 cm2. • 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 cm2.
Working Mode: Scan survey + pointed observation
Orbit: 550 km 43°P/L: ~ 1000 kg
Crab Days Roma 16- 17 October 2008 51PolarixTeam
Astronomical Instr SPIE2008 X-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 52PolarixTeam
Astronomical Instr SPIE2008 X-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 weight 90 kg
Maximum lenght 250 cm
Maximum diameter
35 cm × 2 telescopes
Crab Days Roma 16- 17 October 2008 53PolarixTeam
Astronomical Instr SPIE2008 X-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 54PolarixTeam
Each Telescope
Astronomical Instr SPIE2008 X-ray polarimetry with HXMT
Shell Design Wolter 1
Shell Length 30 cm × 2
Focal length 2.1 m
Number of shells 30
Shell Thickness 100 ÷ 200 μm
Coating Ir + C (only 22 external)
Mounting Spider
Weight of shells 8 ÷ 16 kg
Total weight 41.4 ÷ 49.5 kg
Crab Days Roma 16- 17 October 2008 55PolarixTeam
The Telescope
Crab Days Roma 16- 17 October 2008 56PolarixTeam
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 57PolarixTeam
MT
Telescope Effective AreaA 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 58PolarixTeam
What can we do with HXMT
HXMT can detect a polarization of20% in 106 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 59PolarixTeam
Sensitivity of polarimeter aboard HXMT
Crab Days Roma 16- 17 October 2008 60PolarixTeam
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-Positive measurement: of X-
ray polarization of the Crab ray polarization of the Crab Nebula without pulsar Nebula without pulsar
contamination (by lunar contamination (by lunar occultation, Weisskopf et al., occultation, Weisskopf et al.,
1978).1978). P P = 19.2 = 19.2 ± 1.0 ± 1.0 % %
= 156.4= 156.4oo ± 1.4± 1.4o
But this is only the average measurement But this is only the average measurement The structure is much more complex!The structure is much more complex!
PSRPSR
NW jetNW jet
SE jetSE jet
Inner torusInner torus
Outer torusOuter torus
With XPOL we can perform the separate With XPOL we can perform the separate polarimetry of details of the major structurespolarimetry of details of the major structures
f.o.v.f.o.v.
IXO IXO p.s.f.p.s.f.
How turbulent is the field?How turbulent is the field?
How polarized is the PSR?How polarized is the PSR?
This iThis is much better than any pathfinder!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 27th - 30th, 2009
Centro Studi AmericaniVia 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.)
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