Crab Days Roma 16- 17 October 2008 1 PolarixTeam X-Ray Polarimetry Programs in Italy Enrico Costa...

Crab Days Roma 16- 17 October 2008 1PolarixTeam

X-Ray Polarimetry Programs in Italy

Enrico CostaIASF-INAF Roma


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


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


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


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.


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


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€).


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.


•Three modules are available (@ OAB - Merate) from Jet-X mission.

•Advantages: low costs

•Disadvantage: high mass

Available TelescopesAvailable Telescopes

HEWHEWmeasmeas = 15 arcsec = 15 arcsec


• 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


• 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)


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)


GEM electric field

pixel

GEM

20 ns

a E

X photon (E)

ASIC

conversion gain

collection

2cos

The Gas Pixel Detector


• 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


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


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


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


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


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


Imaging capability

Holes: 0.6 mm diameter, 2 mm apart.

55Fe source Ne(50%)-DME(50%)


5.4 keV polarised photons (Cr)5.4 keV polarised photons (Cr)5.4 keV polarised photons (Cr)


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%


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.


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


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


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.


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


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


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


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


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


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


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.


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


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


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


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


POLARIX


POLARIX

MISSION ANALYSIS1/

VEGA PERFORMANCES


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.


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.


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)


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


Sensitivity


Angular Resolution: resolving the Crab


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


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.


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



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.



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



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.


Each Telescope


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


The Telescope


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.


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).


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!


Sensitivity of polarimeter aboard HXMT


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.)

Crab Days Roma 16- 17 October 2008 1 PolarixTeam X-Ray Polarimetry Programs in Italy Enrico Costa...

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Transcript of Crab Days Roma 16- 17 October 2008 1 PolarixTeam X-Ray Polarimetry Programs in Italy Enrico Costa...