High Energy, High Resolution X-Ray Spectroscopy Eric Silver

1. High Energy, High Resolution X-Ray Spectroscopy Eric Silver Harvard-Smithsonian Center for Astrophysics Photon Energies > 10 keV Measurements Important to Astrophysics, Atomic and/or Nuclear physics Two Science Topics Nuclear Line Astrophysics QED Related Heavy Ion Spectroscopy USE MICROCALORIMETERS

2. Nuclear Line Astrophysics Direct probe of one of the most violent events in the universe a Supernova explosion that expels the heavy elements into the ISM from the nuclear furnace in which they were created 44Ti is a key diagnostic Produced deep in the stellar core 60 year half-life longer than the few years required for the overlying strata to become optically thin at high energies sufficiently short that the 44Ti remains localized around the SN site while it emits intensely Model calculations of nucleosynthesis yields for Type Ia and Type II SN show that conditions for 44Ti production are significant only within the central cores of massive stars or in white dwarfs following a surface detonation. Mass of 44Ti is an important diagnostic of the most extreme densities and temperatures.

3. 1157 keV line detected by (CGRO)/COMPTEL (Iyuden et al.1994) Flux of (3.3 ±0.6) x 10-5ph cm-2 s-1 44Ti Decay Scheme Detection of the 67.9 and 78.4 keV Lines in Cas A by Phoswich Detection System aboard BeppoSAX Vink et al. 2001 Flux of (2.1 ±0.7) x 10-5 ph cm-2 s-1 Initial 44Ti mass of (0.8 – 2.5) x 10-4 MΘ

4. High Energy Microcalorimeter Silver, E., et al., 2002, AIP Conference Proceedings, Volume 605, 555.

5. Modest Focusing Multilayered Optics Low Background Microcalorimeter High Spectral Resolution

6. Thin Foil Plastic Optics The telescope needs to being nothing more than a “light bucket” with a HEW ~ 4 arcmin. work with the prototype conventional optic. (Schnopper et al. 2003) Requirements can be easily met. The folded scattering curve predicts a HEW of 34 arcsec for single reflection telescope made from this plastic. Expected HEW if the telescope was built perfectly, i.e., there are no figure errors

7. Modest focusing (<4 arc min), multilayered optics to reduce the background and enhance the effective area in a balloon-borne experiment A 20 x 20 array of microcalorimeters with 50 eV resolution 3 σ narrow line sensitivity at 68 keV is 3.3 a 10-7 ph cm-2 s-1 in 106 s; 50 times more sensitive than INTEGRAL

8. Sufficient spatial and spectral resolution to determine the extent and the velocity distribution of the 44Ti emitting region Non-X-ray background is almost 3 orders of magnitude less than typically achieved in this energy region

9. t = C / G Recent Technical Advances X-Ray Microcalorimeters Soft X-Ray detectors Reduced readout noise 3 eV at 6 keV (60 mK) Consistent with model calculations Absorber Thermistor Aluminum Wires Heat Sink Tantalizing Outlook for high energies Earlier measurement (80 mK) 50 eV 30 eV Use soft x-ray thermistor(60 mK) Larger R and dR/dT S/N increases Larger volume x-ray absorbers may improve Q.E. 4-fold

11. Novel Conical Spiral for Astronomy Single Reflection (ε = 60%) 1.6 x Reflection efficiency of 2 reflections X-ray Optics Small Cylindrical Spiral Lenses For the Laboratory This large spiral prototype lens is wound with seven turns of W coated PET plastic. Twenty-four ribs in the front and back wheels support a 50 mm wide, single strip of plastic. The pins are 1.27 mm in diameter and the spacing between the shells is 2 mm. A 6 in scale is placed in front of the lens. Potential Increase in Collecting Area 4-5 times (detector efficiency) 1.6 times (reflection) 6.4 – 8 (Total)

12. Flight Program Test flight of optics in September 2005 aboard MSFC gondola Seeking support to finish microcalorimeter array and electronics To be incorporated in Ball Aerospace lightweight dewar Cas A 20 days Fairbanks, Alaska

13. QED : Basis and cornerstone of all present field theories Enormous success in predicting properties of electrons in weak fields However A precise test is still pending for strong field limit where new phenomena may appear Comparison of predictions and experimentally determined energy levels of strongly bound electrons provides a critical test of QED UNILAC ESR SIS N Ion 108 GSI-Accelerator Facility UNILAC 11.4 MeV/u U73+ 10 - 500 MeV/u U92+ up to 1000 MeV/u U92+

14. Atomic Physics in Extremly Strong Coulomb Fields H-like Uranium EK = -132  103 eV <E>= 1.8  1016 V/cm Self Energy Z = 92 Quantum Electro- Dynamics Vacuum Polarization Z = 1 Hydrogen EK = -13.6 eV <E>= 1  1010 V/cm 1s-ground state: increase of the electric field strength by six orders of magnitude

15. 2p3/2 Ly α1(E1) -34.1 keV 2p1/2 -34.2 keV Ly α2(E1) -131.8 keV QED -132.2 keV Dirac The Structure of One-Electron Systems QED Corrections ∆E ~ Z4 / n3 Z: nuclear charge number N: principal quantum number Large relativistic effects on energy levels and transition rates (e.g. shell and subshell splitting) Large QED corrections Transition energies close to 100 keV Atomic systems at high Z

16. Current Status ∆E (β) ∆E (fit) ∆E (geometry) Ly α1 ± 2.6 eV ± 9.7 eV ± 8.5 eV 102170.7 ± 3.2 Stöhlker et al. Phys. Rev, 85, 15, 2000 What can the microcalorimeter add? A Self-Calibrating Measurement ! Better Energy Resolution ! E proj = γ ( 1 – β cos Θlab ) E lab Determined from the Balmer spectroscopy of line energies known to 0.1 eV Ultimately, precision can be 1 eV or better

17. X-Ray Studies for Au 78+ Commissioning of a Microcalorimeter at the ESR Storage Ring Silver, E., et al., 2003, Nuclear Instruments and Methods in Physics ResearchA 520, 60. Microcalorimeter + EMI shield installed at ESR Spectrum obtained during parasitic beam time in March 2003

18. Analysis Au78+ 3d5/2 – 2p3/2 12.161 keV (rest) Microcalorimeter 7.98 ± 0.01 keV Doppler correction = 0.656 ± 0.0016 Scale Ly α1 escape @ 21.8 keV after adding Sn Kα = 25.196 keV 46.99 keV (lab) 71.63 ± 0.106 keV (rest) Note: Ly α1 corrected for QED = 71.570 keV (Beier et al. 1997)

19. Next Experimental Campaign 3 Detectors 16 detectors 5.3 x 520 mm 220 mm 5.6 x 145° 90° ; SA correction 0.652 0.8962 1.9 x Total increase in rate 56.3 x (SA 5 x 10 -8 sr 2.6 x 10 -6 sr)