1. X-Ray Spectroscopy

2. 1 eV 100 eV 10 eV Energy (keV) The need for high resolution X-ray spectroscopy Astrophysical Plasmas: Simulation of the emission from a gas at T = 10 7 K with normal abundances of elements. An energy resolution of ~ 10 eV is required to begin serious X-ray spectroscopy and a resolution of ~ 1 eV is required for complete plasma diagnostics and velocity measurements.

4. What’s a milliCrab? The second brightest X-ray (1-10 keV) source in the sky is the Crab nebula Its photon intensity at the top of the atmosphere of the Earth is ~ 10 cm -2 s -1 There are about 1000 AGN (“quasars”) at a level of about.01 cm -2 s -1 = 1 mC

6. He-like H-like ionized Oxygen Shock-Heated to kT ~ 0.3 keV Ionization age

7. X-Ray Spectrum with 100 eV Resolution Cassiopeia A ACIS spectrum 4-6 keV

11. Estimates of H- and He-Like Energies vs Atomic Number

12. X-Ray Spectrometers - I Proportional counters have –High efficiency –Imaging capability –Multiplex spatial/spectral without confusion But resolving power ≡ E/(δE) ≈ 6√E(keV)

15. X-Ray Spectrometers - II Bragg crystal spectrometers –Dispersive, so they can use any detectors –Can achieve R > 10 3 –Can have high efficiency (at one E at a time) But no imaging or multiplexing capabilities (i.e. can look at only one E at a time)

17. X-Ray Spectrometers - III Gratings –Dispersive –Can have moderate (few %) efficiencies –Can multiplex (all E at the same time) –Can have R > 10 3 /√E(keV) (better for low E) But image and spectral orders are mixed

18. Capella Chandra HETG

19. X-Ray Spectrometers - IV Solid State (including CCDs) –High efficiency (>90%) –Non-dispersive, can multiplex all E –Imaging capability without confusion with E But cannot achieve better than R ≈ 25√E(keV) (Resolution ≈ 40√E(keV) eV)

20. 1 eV 100 eV 10 eV Energy (keV) The need for high resolution X-ray spectroscopy Astrophysical Plasmas: Simulation of the emission from a gas at T = 10 7 K with normal abundances of elements. An energy resolution of ~ 10 eV is required to begin serious X-ray spectroscopy and a resolution of ~ 1 eV is required for complete plasma diagnostics and velocity measurements.

21. X-Ray Spectrometers - V Cryogenic Microcalorimeters –High efficiency (>90%) –Non-dispersive, can multiplex all E –Imaging capability without confusion with E And can achieve R > 10 3 √E(keV)

22. Physical Conditions Through X-Ray Spectroscopy Fe-K lines provide very clean diagnostics. One such diagnostic: excellent density-independent temperature sensitivity in the range 10 7 –10 8 Kelvin. x y z w He-like Fe “triplet” Energy (keV) Counts Expected with XRS (12 eV) Chandra HEG (~ 60 eV) w y, x z Neutral Fe He-like Fe H-like Fe

23. The X-ray Microcalorimeter Features high resolution, non-dispersive spectroscopy with high quantum efficiency over K- and L- atomic transition band. Moseley, Mather and McCammon 1984

24. Simple Energy Resolution Argument δT = E/C (temperature rise for E deposition) C ≈ N(kT)/T (N = # of phonons with ) N ≈ C/k (fluctuation in N is the “noise”) ΔN = √N (Poisson statistics) R = E/(ΔE) (resolving power) ΔE ≈ kT√N ≈ kT√(C/k) ≈ √(kT 2 C) More carefully, ΔE = 2.35 ζ √(kT 2 C)

25. Spectral Resolving Power: Depends on thermometer technology Temperature-sensitive resistance Resolution limited by thermal fluctuations between sensor and heat bath and Johnson noise. Doped semiconductor Superconducting Transition T = operating temperature (50-100 mK) C = heat capacity  ~ 2 - 4 for doped semiconductors ~ 0.2 for transition edge sensors For both thermometer schemes a spectral resolution of few a eV is possible! R (ohms) Temperature

26. Types of thermometers: resistive capacitive inductive paramagnetic electron tunneling Basic requirements: Low temperature Sensitive thermometer Thermal link weak enough that the time for restoration of the base temperature is the slowest time constant in the system yet not so weak that the device is made too slow to handle the incident flux. Absorber with high cross section yet low heat capacity Reproducible and efficient thermalization

27. ...... Microcalorimeter Arrays XQC Array: 36 array of 0.5  2 mm pixels.

28. X-Ray Quantum Calorimeter Dewar

31. E Energy (keV) 6.4 eV FWHM Ion beam 1.5  m ~ 6 times deeper thermometer (after anneal) Deep implants using silicon-on-insulator wafers. 625  m pixels Mn K   Mn K   GSFC

35. RTS – Rotating Target Source continuum X-ray source X-ray continuum X-ray lines targets (one is open for continuum) rotating target wheel

36. target wheel motor