at the MPE test facility PANTER

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1 Calibration of hard X-ray (15 50 kev) optics at the MPE test facility PANTER M. Freyberg, H. Bräuninger, W. Burkert, G. Hartner Max-Planck-Institut für extraterrestrische Physik, PANTER X-ray Test Facility, Gautinger Straße 45, Neuried, Germany O. Citterio, F. Mazzoleni, G. Pareschi, D. Spiga INAF - Osservatorio Astronomico di Brera, Via Bianchi 46, Merate (Lc), Italy S. Romaine, P. Gorenstein Harvard-Smithsonian CfA, Cambridge,MA,USA B. Ramsey NASA/MSFC, National Space Science and Technology Center, Huntsville, AL, USA

2 Outline the MPE test facility PANTER: a general description possible PANTER set-ups in hard X-rays: monochromatic and energy dispersive modes effective area characterization of a single-cone multilayer-coated mirror shell up to 50 kev summary & conclusions

3 The MPE test facility PANTER: an artificial point-like X-ray X star for enabling full-illumination tests of astronomical optics The ideal way for testing X-ray optics is to create an artificial point-like X-ray star at infinite distance, which corresponds to provide a large collimated parallel beam of X-rays Since optics producing collimated and uniform X-ray beams are very hard to build, the easiest way to meet the above requirements is to put a point-like isotropic X-ray source as far as possible in front of the mirror system. 2 L L Z0 p = 1st surface height Z 0 = F.L. P rms = 4 tanα p = distance fom the source Z0 p a = inc. angle In the case of the PANTER test facility the distance between X- ray source and optics is 125 m ( entrance of the test chamber) X-ray source X-ray optics 125 m

4 PANTER: an unique X-ray X test facility in Europe the facility was initially developed for the X-ray calibration of the ROSAT telescope almost all X-ray missions, besides ROSAT, have been tested at the facility Beppo-SAX, JET X, SOHO/CDS, ABRIXAS, Chandra LETG, XMM-Newton, SWIFT XRT, Suzaku mirror and material studies for future missions like XEUS, ROSITA, Constellation-X in recent years, in collaboration with the OAB-INAF several prototypes of light-weight monolithic X-ray mirror shells made of ceramic materials have been measured at PANTER. The enabling of the calibration of hard X-ray optics (from 15 up to 50 kev and beyond) in view of future hard X-ray space missions and balloon experiments based on focusing mirrors is mandatory.

5 PANTER s architecture the experiments are placed in a big vacuum chamber (12.5 m long and 3.5 m in diameter). They can be moved and rotated by means of manipulators driven by stepper motors, with a typical accuracy of 3 microns and 1 arcsec, respectively. the X-ray source and the chamber are connected with a tube of 1 m in diameter. X-ray source, tube and chamber are kept under high vacuum, at a pressure of ~10-6 mbar, by means of 4 independent pumping stations. at the chamber 2 big cryo-pumps, with a pumping capacity of liters/sec each, reduce the partial pressure of water vapor in the rest gas by a factor of ten or more, to avoid icing on the cooled CCD cameras.

6 X-ray sources at PANTER Four different X-ray sources are available at PANTER. The X-ray sources are mounted on a rail system and changes between them are done within a couple of hours: the main source is an open one using a target wheel: 16 different targets (elements) can be chosen giving the characteristic X-ray lines of that element in an energy range between 0.28 kev (C-K) and 8.05 kev (Cu-K). to get very high fluxes, a commercial (sealed) X-ray source may be the choice. It provides a couple of X-ray lines between 4.5 kev and 22 kev. Since this source provides high voltages up to 60 kv, it can cover an energy range from 4.5 to 50 kev using the bremsstrahlung continuum component of the emission spectrum. two X-ray monochromators are installed as well: a tunable reflection grating monochromator covering an energy range from 0.2 to 1 kev (or up to 2 kev, using the second orders). a double crystal monochromator, also tunable, providing photon energies between 1.5 and 25 kev. The energy resolution of both systems is 4% or better

7 X-ray detectors at PANTER a spare model of the ROSAT PSPC (Position Sensitive Proportional Counter), with moderate energy and spatial resolutions (30% and 250µm at 1.5 kev, respectively) but, since it is an exact photon counting device, it is best suited for measuring effective areas of X-ray mirrors. Its wide field of view (80 mm in diameter) makes this detector also very useful for measurements of mirror scattering and alignment procedures. a spare model of the EPIC pn-ccd camera aboard XMM-Newton with an excellent energy resolution (145 ev at 6 kev) and also a good spatial resolution (pixel size 150µm). Since this camera still performs 3% efficiency at 50 kev it can also be utilized for the hard X-rays. Its collecting area is 60x60 mm 2. a CCD camera with a pixel size of 27µm. This camera is a predecessor of the EPIC MOS camera aboard XMM-Newton and works between 0.2 kev and 8 kev. The camera is a contribution of the University of Leicester, UK. it is planned to install a follow-up model of the pn-ccd camera with improved properties like energy and spatial resolution. This camera is under development at the MPE for future missions (e.g. DUO/e-ROSITA).

8 Hard X-ray X measurements in monochromatic mode The monochromatic X-ray source consists of a tube-monochromator complex integrated into a vacuum chamber: a special water-cooled X-ray tube of an open type with changeable anode targets (Cu and Mo) a voltage up to 50 kv and a current up to 60 ma can be set a double crystal monochromator. It has the rotation axis in the middle point of the first crystal, a so-called fixed exit system 3 possible choices of crystals: Si (111), KAP (100) and HOPG (002). HOPG mosaic crystals are in general used for the high reflection efficiency (lower limit: 2 kev)

9 Use of the mono system beyond 10 kev the 2 nd Bragg peak is used E/E < 3 % for the 2 nd Bragg peak Flux: ~300 ph/cm 2 /s at the chamber entrance

10 Test in monochromatic mode of a multilayer-coated single-cone shell up to 20 kev XMM FM#5 Mirror shell diameter: 121 mm Focal length: 3.6 m single-cone ML shell Single-cone Ni-replicated shell Coating: Ni/C 12 bilayers Effective area in good agreement with a model taking into account the initial mandrel microroughness Effective Area (cm 2 ) SAX # 12 Ml mirror Effective Area (single-cone) Photon Energy (kev) 20

11 Hard X-ray X measurements in energy-dispersive mode a very easy way to operate the facility in hard X- rays is in the so-called energy dispersive mode: a broad-band beam illuminates the optics to be tested in this case one makes use of the pn-ccd camera with its very good energy resolution (~ 2.5 % at 6 kev and improving proportionally to the square root of the photon energy); it is in any case sufficient for testing hard X-ray optics use of a commercial sealed source with W anode. It can cover an energy range from 4.5 to 50 kev using the bremsstrahlung continuum component of the emission spectrum the achievable flux at the entrance of the test chamber can be as large as 3500 photons/cm 2 /s in the kev energy range, depending on the source settings.

12 The EPIC pn-ccd quantum efficiency Photon Energy 10 kev 20 kev 30 kev 40 kev 50 kev Quantum Efficiency 89.1 % 25.1 % 8.6 % 4.7 % 3 % The QE tends to rapidly decrease with the photon energy beyond 15 kev. But it is still sensitive up to 50 kev. Flux (photons/mm 2 /s) Photon Energy (kev) 40

13 Hard X-ray X test of a multilayer coated single-cone shell in energy-dispersive mode: a first test to prove the concept single-cone shell prototype realized in the context of the development of the Hard X-ray Telescope for the Constellation X mission shell (Ø = 280 mm, H = 150 mm) not uniformly coated, but sectors with different ML films W/Si multilayer 20 bilayers, d-spacing = 78 Å, Γ = witness multilayer sample was realized during the same run onto a GO superpolished 2" disk N = 20, d-spacing = 75 Å, Γ = 0.3. Also the witness sample, for comparison, was tested at PANTER. Maximum Diameter Focal length Mirror height On-axis incid. angle 280 mm mm 125 mm 0.21 deg

14 Set-up used to perform the measurement of the mirror-shell and the witness flat A 4 mm (diam.) hole was also precisely drilled in the screen to allow the measurement of the direct beam

15 The mirror shell, once integrated, was mounted at the entrance of the testing chamber onto the manipulator

16 Direct beam Photons reflected by the mirror shell

17 Results from measurements test successfully performed up to 50 kev Mirror shell up to 50 0' (12'.65) Mirror +2' Mirror +4' Mirror +6' Mirror +8' Simulation 0.7 as expected, due to the different roughness levels of the starting substrate, the reflectivity of the witness sample is larger than that of the mirror shell the reflectivity profiles taken in energy dispersive mode were then fitted by assuming a proper model for the interfacial roughness and the multilayer parameters 1.0 Measured reflectivity IMD simulation 1.0 Meas. at grazing angle 14'.65 IMD simulation Reflectivity Reflectivity Energy (KeV) Energy (KeV)

18 Pencil beam measurements The mirror shell and the the witness sample were successively measured at OAB with a pencil beam 8 and 17 kev photon energies 10 0 Measured Reflectivity at 8 KeV IMD simulation 10 0 IMD simulation Measured reflectivity at 8 KeV Reflectivity Reflectivity Grazing Incidence Angle (arc sec) - angular resolution 25'' Grazing Incidence Angle (arc sec) - angular resolution 25'' IMD simulation Measured Reflectivity at 17 KeV IMD Simulation Reflectivity 17 KeV Reflectivity (after noise subtraction) Reflectivity Grazing Incidence Angle (arc sec) - angular resolution 15'' Grazing Incidence angle (arc sec)

19 Comparison of the results Shell (Pencil beam) Shell (PANTER) Witness (Pencil beam) Witness (PANTER) 8 kev 17 kev kev 8 kev 17 kev kev Period (Å) Gamma factor Si/W interface roughness (Å) W/Si interface roughness (Å) The results obtained at PANTER in the energy dispersive set-up and at OAB in pencil-beam mode are in substantial good agreement to each-other

20 First test at full illumination of a Wolter I optics (Oct 2004) Profile Diameter Length Incidence angle at 8 Focal Length Nickel walls thickness Coating Wolter I 27 cm 40 cm m 0.2 mm Pt/C ML *

21 Preparation of the Panter/MPE X A special manipulator was prepared by OAB for alignment inside the vacuum tube Horizontal alignment 2. Vertical alignment Other movements 4 X 3

22 Geometrical effects due to the finite distance of the X-ray source The X-ray source distance from the optics (125 m) give rise to a (small) divergence of the beam Angle between the incoming X-ray beam and the optical axis = 0.06 q inc parabola = 0.25 q inc hyperbole = 0.13 Longher Focal length: FL = m instead of 10 m FL ~ 50% of the parabola lost because unable to intercept the hyperbola surface: Lost Fraction :

23 Angular resolution HEW ~ kev (i.e. in agreement with the mandrel profile) HEW ~ kev due to scattering

24 Effective area results PSPC data - calibration lines C_K (0.27 kev) Cu_L (0.93 kev) Al_K (1.49 kev) Ti_K (4.51 kev) Cr_K (5.41 kev) Fe_K (6.40 kev) Cu_K (8.04 kev) High Energy (10 40 kev) EPICpn data: obtained by operating the calibration in energy dispersive mode (bias of 45 kev + Ti filter)

25 Fit of the Effective Area data The source finite distance effects (2 different incidence angles) must be taken into account θ inc = 0.25 o X θ inc = 0.13 o

26 July 2005 Test of a MSFC NiCo shell integrated at INAF/OAB W/Si multilayer coating (N=95) performed at CfA (shutter open) NiCo: 150 µm thick 23 cm diameter 42.6 cm long Coated with: graded-d ML

27 PSPC Data: Surface Brightness Cu-K 8.04 kev Fe-K 6.40 Ti-K 4.51 Al-K 1.49 Cu-L 0.93

28 PSPC Data: Radial Profile Cu-K 8.04 kev Fe-K 6.40 Ti-K 4.51 Al-K 1.49 Cu-L 0.93

29 PSPC HEW (50% diameter) Energy (kev) 0.93 HEW (arcsec) Notes: High energy HEW (ccd) intensity too high pileup

30 Panter Data + Model linear logarithmic R p =0.218 deg R h =0.111 deg Rh * Rp Energy (kev) Energy (kev) PSPC pn-ccd (30 kv) pn-ccd (50 kv) (0.2 8 kev), discrete points (*) (13-50 kev), continuum (, ) Model = solid line, fit to 10 Å roughness (using IMD software package of D. Windt)

31 Test of very long focal length optics 1 m Imaging test SX with a pencil beam * * X-ray source Pin-hole F.P. X-ray telescope ~1x1mm aperture * At e.g. 30 m (Simbol-X focal length baseline), due to the finite distance of the X-ray source, the percentage of photons undergoing the second reflection will be negligible in the full illumination mode!

32 Conclusions the PANTER facility, with very small changes of the usual setup and the utilizing hardware components already available, can be used also in the hard X-ray band, up to 50 kev photon energy. This is a very important implementation enabling the characterization of hard X-ray telescopes. for optics with focal lengths larger than 8-9 m the optics to be tested can be mounted directly into the vacuum tube by means of jigs two possible set-ups: monochromatic (up to 25 kev) and energy dispersive (up to 50 kev) for very telescope with long focal length (e.g. Simbol-X) special set-up have to be investigated.

33 END