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VOXES: A New High-Resolution X-ray Spectrometer

VOXES aims to develop an ultra-high resolution X-ray spectrometer using bent HAPG crystals for low-yield measurements in high-background environments. The project targets precise X-ray measurements ranging from 2-20 keV in various fields. Challenges include non-linear Bragg spectrum and efficiency loss due to mosaic crystals.

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VOXES: A New High-Resolution X-ray Spectrometer

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  1. VOXES, a new high resolution X-ray spectrometer for low yield measurements in high background environments X O S E Alessandro Scordo Laboratori Nazionali di Frascati, INFN • 2nd Jagiellonian Symposium on Fundamental and Applied Subatomic Physics – Krakow, 9th June 2017

  2. 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, the realisation of such X-ray detector systems able to work in highbackground environments is badly needed. • Usually, X-rays of our interest don’t come from a point-like source; it is mandatory to explore the possibility to work 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 in high background environments with ‘extended’ sources High resolutionvon-HamosX-Rayspectrometerusing HAPG for Extended Sources in a broadenergyrange

  3. An example: 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. (6→5) kaonic nitrogen transition: 7560± 32 eV, (7→6) kaonic nitrogen transition: 4589± 37 eV. http://pdg.lbl.gov/2015/reviews/rpp2014-rev-charged-kaon-mass.pdf Exploratory test with DEAR @ DANE Not yet performed Calculated efficiency ~ 400 times less than @ DAFNE Un-efficient background reduction (statistics loss)

  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 ~ 1 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) TC ~ 50 mK !!!

  7. High resolution can be achieved depending on the quality of the crystal and the dimensions of the detectors Geometry of the detector determines also the energy range of the spectrometer nl = 2dsinqB 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 Background reduction capability is mandatory Typical d (Si) ≈ 5.5 Å qB < 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 Pyrolitic Graphite mosaic crystals (d = 3.354 Å): Highly Oriented Pyroliltic Graphite (HOPG, Dq≈1°) Highly Annealed Pyrolitic Graphite (HAPG, Dq≈0.05°) flexible HAPG has twice higher spectral resolution, while flexible HOPG – approximately twice higher reflectivity

  9. Von Hamos configuration r r r = 206,7 mm Cu (Ka1) = 8048 eV  qB = 13.28° g path ≈ 180 cm evH/eflat ~ rθ/a radius of curvature angular aperture source size • PRO: • Focusing • Energy rangegiven by the crystal • Distance from the source (background….) • Perfect (linear) Braggspectrum • CON: • Absorption in air • ‘Point-like’ source needed (low geom. eff.)

  10. Johann configuration Rowlandcircle (r) Curvedcrystal with r = 2r • PRO: • Higherefficiency (geometrical, distance from source…) • No ‘point-like’ source needed • Lessabsorption in air r = 206,7 mm Cu (Ka1) = 8048 eV  qB = 13.28° g path ≈ 10 cm • CON: • Non linear Braggspectrum (unlessusingcurved detectors….) • Near to source (background) • No verticalfocusing (partiallyrestore with sphericalcrystals) • Energy rangefixed by the target

  11. Starting VOXES: test Setup Designed & 3D-printed @ LNF Dectris Ltd MYTHEN2 detector: 32 x 8 mm surface 640 channels  50 mm resolution 4-40 keV range Working @ room temperature

  12. Location for VOXES development

  13. Starting VOXES: first tests with HAPG crystals First stage measurements: • Ti, Cu, Br, Zr (activated with X-Ray tube) • X-raydetection with MYTHEN2 (Dectris Ltd, Zurich) • Differentrcrystals (10.6 mm & 206.7 mm) • Differentthickness (20,40,100 mm) r = 10.6 mm 100 mm r = 206.7 mm 20 mm r = 206.7 mm 40 mm r = 206.7 mm 100 mm

  14. MC simulations (running…) Open questions: • Johann or Von Hamos? • whichr ? • Whichis the efficiency of the X-ray source? Johann Von Hamos

  15. First spectrum with Cu Ka lines First measurement conditions: 206,7 mm r, 100 mm thickness, 9.6 cm2 surface XZ opening angle : Dq = 0.2° Beam on HAPG is 3 mm (X spread) qB = 13.28° (Ka1 line = 8047,78 eV) Von Hamos configuration Z X 1 hour data taking X spread ≈ 60 channels ( 60 x 50 mm = 3 mm)

  16. First spectrum with Cu Ka lines Very preliminary 12 hours (X-ray tube off) 12 hours (X-ray tube on) Amp (Ka1) ≈ 0.5 Amp (Ka2) ∫ Ka1 ≈ 1740 ∫ Ka2 ≈ 875

  17. Quality check measurement @ PSI T. van EGIDY and H. P. POVEL Nuclear Physics A232 (1974) 511- 518; pM1 Line Low momentum p,m (≈ 100 MeV/c) Possible calibration lines

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

  19. Next steps… • Measurement of the pionic atoms transitions at PSI • Fast & triggerable position detectors  Linearly Graded SiPM (FBK) • Parallel measurement of energy & position to improve background reduction & conclusions • The VOXES projectaims to investigate the possibility to use Bragg • spectrometers with diffusedsources and in high background environments • HAPG crystals are idealcandidates for thisporpouse and can be used in differentgeometricalconfigurations (Von Hamos, Johann, ecc…) • Such a spectrometermayhave a strong impact in severalfieldslikenuclear and fundamentalphysics, medical, elementalmapping, astrophysics Thank you for the attention

  20. SPARE

  21. Kaonic helium is formed when a K- is captured in the electron orbit It down cascades toward the lowes levels emitting X-rays To test the influence of the strong interaction the energy a precise measurement of the line shift and width of the 3d->2p transition is needed The discrepancies between different theoretical models and approaches could be eliminated with ~ 1eV precision measurement Best measurements (SIDDHARTA):   4He +5 ±3 (stat.) ±4 (syst.) 14 ±8 (stat.) ± 5 (syst.) 3He −2 ±2 (stat.) ±4 (syst.) 6 ±6 (stat.) ±7 (syst.) New measurements are needed

  22. PG - artificial graphite • Production • Thermo cracking of CH4 • on heated substrate at T=2100oC • Pyrocarbon d002=3,44Å, mosaicity 30o • Annealing under pressure • at T>2800oC • Pyrographite: • HOPG d002=3,356-3,358Å, mosaicity <1o • HAPG d002=3,354-3,356Å, mosaicity <0.1o

  23. Bending does not influence resolution and intensity • Mosaic spread down to 0.05 degree • Integral reflectivity ~ 102 higher than for other crystals • Variable thickness (efficiency) • Excellent thermal and radiation stability Already tested with 500 m slits How much could one go further? Can we use it with diffused sources?

  24. Specific features of HAPG: Peak reflectivity at different reflection orders

  25. Specific features of HAPG: Peak reflectivity for different crystal thickness

  26. Specific features of HAPG: Mosaic spread

  27. Comparison of HOPG and HAPG in (004)-reflection F = 400 mm in (004)-reflection Ge (111)‏ Ge (111)‏ H. Legall, H. Stiel, I. Grigorieva, A. Antonov et al. (unpublished)‏

  28. Comparison of HOPG and HAPG (004) reflection at distance F=400 mm E/∆E=4100 (CuKα)‏ E/∆E=3500 (CuKα)‏ The highest resolution of E/∆E=7000 for (004) reflection at 15 µm HAPG film at distance 1500 mm was achieved H. Legall, H. Stiel, I. Grigorieva, A. Antonov et al., FEL Proc. 2006

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