Development of a high precision X-ray spectrometer for diffused sources with HAPG crystals in the range 2-20 kev: the VOXES experiment O S

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1 ECT*, Trento, 26/10/2017 Development of a high precision X-ray spectrometer for diffused sources with HAPG crystals in the range 2-20 kev: the VOXES experiment X INFN-CSN5 Young Researcher Grant 2015, n /2015. E O S Alessandro Scordo Laboratori Nazionali di Frascati, INFN ASTRA: Advances and open problems in low-energy nuclear and hadronic STRAngeness physics

2 Best measurements (SIDDHARTA): Target The discrepancies between different theoretical models and approaches could be eliminated with ~ 1eV precision measurement 4 He +5 ±3 (stat.) ±4 (syst.) 14 ±8 (stat.) ± 5 (syst.) 3 He 2 ±2 (stat.) ±4 (syst.) 6 ±6 (stat.) ±7 (syst.) New measurements are needed

3 A possible application: the K - mass puzzle K - mass is a fundamental quantity in physics to reduce the electron screening effect Needs precision below 0.1 ev!

4 Project s goal High resolution (few ev) measurements of the X rays (2-20 kev) emitted in various processes is strongly demanded in: particle and nuclear physics, fundamental science, astrophysics, biology, medical and industrial applications Additionally, for some applications (like exotic atoms measurements) X-ray detector systems have to be operated in high background environment. These X-rays not always are produced by a point-like source; it is mandatory to develop detectors working with extended (diffused) sources. VOXES s goal: to develop, test and qualify the first prototype of ultra-high resolution and high efficiency X-ray spectrometer in the range of energies 2-20 kev using HAPG bent crystals able to work with extended sources High resolution von-hamos X-Ray spectrometer using HAPG for Extended Sources in a broad energy range

5 Commonly used detectors for X-rays in the range 1-20 kev are the Solid State Detectors (CCD, SDD, etc ) However The solid state detectors have intrinsic resolution (FWHM ~ 120 ev at 6 kev) given by the electronic noise and the Fano Factor Presently, to achieve ~ ev resolution, two options are available: Transition Edge Sensors (TES) Crystals and position detectors (Bragg spectrometers)

6 Transition Edge Sensors (TES). Excellent energy resolution (few ev at 6 kev) LIMITATIONS: not optimised for E < 5 kev very small active area prohibitively high costs rather laborious use (complex cryogenic system needed) T C ~ 50 mk!!!

7 High resolution can be achieved depending on the quality of the crystal and the dimensions of the detectors nl = 2dsinq B Geometry of the detector determines also the energy range of the spectrometer But. Crystals response may not be uniform (shape, impurities, ecc.) Lineshapes are difficult to be measured within few ev precision (surface scan) In accelerator environments particles may hit the detector Typical d (Si) 5.5 Å Background reduction capability is mandatory q B < 10 for E > 6 kev (forward & difficult) Limitation in efficiency

8 Mosaic crystal consist in a large number of nearly perfect small crystallites. Mosaicity makes it possible that even for a fixed incidence angle on the crystal surface, an energetic distribution of photons can be reflected Increase of efficiency (focusing) ~ 50 Loss in resolution E/ E=4100 (CuK α ) Pyrolitic Graphite mosaic crystals (d = Å): Highly Oriented Pyroliltic Graphite (HOPG, Dq 1 ) Highly Annealed Pyrolitic Graphite (HAPG, Dq 0.07 ) E/ E=3500 (CuK α ) flexible HAPG has twice higher spectral resolution, while flexible HOPG approximately twice higher reflectivity H. Legall, H. Stiel, I. Grigorieva, A. Antonov et al., FEL Proc. 2006

9 Bending does not influence resolution and intensity Mosaic spread down to 0.05 degree Integral reflectivity ~ 10 2 higher than for other crystals Variable thickness (efficiency) Excellent thermal and radiation stability

10 Von Hamos configuration r r r = 206,7 mm Cu (Ka 1 ) = 8048 ev q B = e vh /e flat ~ rθ/a g path 180 cm radius of curvature angular aperture source size PRO: Focusing Energy range given by the crystal Distance from the source (background.) Perfect (linear) Bragg spectrum CON: Absorption in air Point-like source needed (low geom. eff.)

11 Johann configuration Rowland circle (r) Curved crystal with r = 2r r = 206,7 mm Cu (Ka 1 ) = 8048 ev q B = g path 10 cm PRO: Higher efficiency (geometrical, distance from source ) No point-like source needed Less absorption in air CON: Non linear Bragg spectrum (unless using curved detectors.) Near to source (background) No vertical focusing (partially restore with spherical crystals) Energy range fixed by the target

12 Von Hamos configuration L1 r L2 r = 206,7 mm Line (ev) q L1 (mm) L2 (mm) Cu (Ka1) 8047,78 13,28 900,54 876,33 Cu (Ka2) 8027,83 13,31 898,31 874,04 Dq min = 0.03

13 Von Hamos configuration DS M S M S 2 Z d 2 S 0 = X Source S 1,2 = X Slits S M = X Mythen DS M = background X Mythen d 1 d F = point-like source Z distance d 0,1 = Slits Z distance d 2 = Mythen Z distance S 1 0 Dq bkg d 0 X Dq = signal opening angle Dq bkg = background opening angle X ray source Slits HAPG Signal photons Background photons Dq S 0 d F

14 Starting VOXES: test Setup Designed & LNF Dectris Ltd MYTHEN2 detector: 32 x 8 mm surface 640 channels 50 mm resolution 4-40 kev range room temperature

15 Location for VOXES development semi Von Hamos configuration

16 Increasing dynamic range Von Hamos configuration r semi -Von Hamos config. r q Out Of Focusing configuration: Exact focusing is not important within the detector strip length S(q) = S(0 ) / cosq OOF- semi -Von Hamos config. r S(q) = S(0 ) / cosq q

17 semi-vh VH VH vs semi -VH configuration

18 Best spectrum with Cu Ka lines Cu Ka 1 XZ opening angle : Dq = 0.1 Point-like source (S 0 = 0) q B = (Ka 1 line = 8047,78 ev) Cu Ka 2

19 Beam angular spread dependence Source width = 500 mm

20 Source width dependence Dtgq=0.1

21 Relative (reflection) efficiency estimate

22 Reflection efficiency estimate 10.5 mm 2 < A HAPG < 35 mm 2 Mythen surface Y M spread

23 Refl. efficiency: Beam angular spread dependence Source width = 500 mm

24 Refl. efficiency: Source width dependence Dtgq=0.1

25 Alloy: Cu (58%) + Zn(40%) + Pb(2%) Zn Ka1 Zn Ka2 Cu Kb Dq min = 0.37 Line (ev) Line (A) sinq q L1 (mm) L2 (mm) Cu 8905,29 1,39 0,21 11,98 996,49 974,65 Zn 8638,86 1,44 0,21 12,35 966,68 944,16

26 Quality check PSI pm1 Line Low momentum p,m ( 100 MeV/c)

27 New setup and targets for PSI r = 103,4 mm r = 77,5 mm Line (ev) q ev/mm Range (ev) ev/mm Range (ev) Thanks to Doris SMI pc (4-3) 6428,39 16,71 29,79 953,23 39, ,78 pc (4-3) 6435,76 16,69 29,83 954,42 39, ,38 Possible calibration lines

28 HAPG technology development Medical Applications (Mammography) FAIR (exotic atoms) JPARC (K-atoms) X-ray spectroscopy (DA NE- Luce) E X O S Particle and Nuclear Physics PSI (p-atoms) DA NE (K-atoms) Industry, art and Safety: Elemental Mapping Foundations: Quantum Mechanics LNGS (PEP)

29 Next steps Measurement of the pionic atoms transitions at PSI Fast & triggerable position detectors SDD? Linearly Graded SiPM? (FBK) Parallel measurement of energy & position to improve background reduction & conclusions The VOXES project aims to investigate the possibility to use Bragg spectrometers with diffused sources and in high background environments HAPG crystals are ideal candidates for this porpouse and can be used in different geometrical configurations (Von Hamos, Johann, ecc ) Promising and improvable results have been already obtained, measuring Cu Ka lines with 10 ev resolution (FWHM) and 0.01 ev precision Such a spectrometer may have a strong impact in several fields like nuclear and fundamental physics, medical, elemental mapping, astrophysics Thank you for the attention

30 Spare

31 (6 5) kaonic nitrogen transition: 7560± 32 ev, (7 6) kaonic nitrogen transition: 4589± 37 ev. Exploratory test with DA NE Not yet performed Calculated efficiency ~ 400 times less DAFNE Un-efficient background reduction (statistics loss)

32 Angular spread and attenuation q S(q) = S(0 ) / cosq

33 Angular spread and attenuation

34 Angular spread and attenuation q S(q=78 ) = S(0 ) / cos(78 )

35 Angular spread and attenuation Protective layer 12 mm Mylar

36 Angular spread and attenuation q Incindent (VH) angle q mm thickness (optimized for 6-8 kev)

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41 Direct measurement (t daq = 30 m)

42 Bragg measurement (t daq = variable) Dtgq= mm HAPG 40 mm HAPG 20 mm HAPG

43 Bragg measurement (t daq = variable) Dtgq= mm HAPG 40 mm HAPG 20 mm HAPG

44 Bragg measurement (t daq = variable) Dtgq= mm HAPG 40 mm HAPG 20 mm HAPG

45 Efficiency evaluation Dtgq= mm HAPG 40 mm HAPG 20 mm HAPG 10.5 mm 2 < A HAPG < 35 mm 2

46 Efficiency evaluation Dtgq= mm HAPG 40 mm HAPG 20 mm HAPG

47 Efficiency evaluation Dtgq= mm HAPG 40 mm HAPG 20 mm HAPG