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

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 44 Ti 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 44 Ti 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 44 Ti production are significant only within the central cores of massive stars or in white dwarfs following a surface detonation. Mass of 44 Ti is an important diagnostic of the most extreme densities and temperatures.

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

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

Modest Focusing Multilayered Optics Low Background Microcalorimeter High Spectral Resolution

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 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. Thin Foil Plastic Optics

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 ph cm -2 s -1 in 10 6 s; 50 times more sensitive than INTEGRAL

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

Recent Technical Advances Microcalorimeters Soft X-Ray detectors Reduced readout noise 3 eV at 6 keV (60 mK) Consistent with model calculations Absorber Thermistor Heat Sink Aluminum Wires  = C / G X-Ray 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

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. 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 Potential Increase in Collecting Area 4-5 times (detector efficiency) 1.6 times (reflection) 6.4 – 8 (Total)

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

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 GSI-Accelerator Facility UNILAC SIS ESR 11.4 MeV/u U MeV/u U 92+ up to 1000 MeV/u U 92+ UNILAC N Ion  10 8

1s-ground state: increase of the electric field strength by six orders of magnitude Atomic Physics in Extremly Strong Coulomb Fields Z = 92 H-like Uranium E K = -132  10 3 eV = 1.8  V/cm Hydrogen E K = eV = 1  V/cm Z = 1 Quantum Electro- Dynamics Self Energy Vacuum Polarization

The Structure of One-Electron Systems 2p 3/2 2p 1/2 Ly α 1 (E1) Ly α 2 (E1) QED Dirac keV keV keV keV QED Corrections ∆E ~ Z 4 / n 3 Z: nuclear charge number N: principal quantum number Atomic systems at high Z Large relativistic effects on energy levels and transition rates (e.g. shell and subshell splitting) Large QED corrections Transition energies close to 100 keV

Current Status ∆E (β) ∆E (fit) ∆E (geometry) Ly α1 ± 2.6 eV ± 9.7 eV ± 8.5 eV ± 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 Θ lab ) E lab Determined from the Balmer spectroscopy of line energies known to 0.1 eV Ultimately, precision can be 1 eV or better

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 Research A 520, 60. Spectrum obtained during parasitic beam time in March 2003 Microcalorimeter + EMI shield installed at ESR

Analysis Au78 + 3d 5/2 – 2p 3/ keV (rest) Microcalorimeter 7.98 ± 0.01 keV Doppler correction = ± Scale Ly α keV after adding Sn Kα = keV keV (lab) ± keV (rest) Note: Ly α 1 corrected for QED = keV (Beier et al. 1997)

Next Experimental Campaign 3 Detectors16 detectors 5.3 x 520 mm220 mm5.6 x 145°90° ; SA correction x Total increase in rate 56.3 x (SA 5 x sr 2.6 x sr)