1. X-Ray Pulse Height Analysis on ASDEX Upgrade
Max-Planck-Institut für Plasmaphysik, EURATOM Association
X-Ray Pulse Height Analysis
on ASDEX Upgrade
A. Weller B. Huber, J. Belapure, T. Pütterich,
M. Sertoli, A. Gude, R. Neu, R. Dux, W. Suttrop,
and the ASDEX Upgrade Team
Max-Planck-Institut für Plasmaphysik, IPP-Euratom Assoc.,
D Garching, Germany
38th EPS Conference on Plasma Physics 27 June – 1 July 2011, Strasbourg, France, Paper P5.054

2. 1. Abstract
● the Soft X-ray (SX) Pulse Height Analysis (PHA) Systemwas refurbished in 2010
● the new Silicon Drift Detector (SDD) in combination with a pulse reset preamplifier
and a state of the art digital signal analyzator allows to process pulse rates
of up to 500 kcps (1 central line of sight)
● particular aims:
▶ provide X-ray survey spectra from plasma core
with emphasis on tungsten (AUG PFCs W-coated [1])
▶ cross calibration of X-ray spectrometers & cameras
● initial results:
▶ core radiation typ. dominated by tungsten M-lines
▶ PHA results well consistent with SX cameras
▶ W concentration derived with SX cooling rates
▶ first observation of tungsten L-lines from high ionized states up to W65+
in hot thin plasmas (Te up to 18 keV)
▶ detection & quantitative analysis of small metal
impurity contaminations (Ti, Cr, Fe, Cu)
▶ Argon impurity analysis allows comparison with
Bragg- and Johann spectrometer data
▶ Te analysis from slope of continuous spectra

3. with cap and Be-Window in TO8 housing
2. Experimental Setup
Detector Response
Silicon Drift Detector (SDD )
from PNDetector
with cap and Be-Window in TO8 housing
● Active volume: 10 mm2 x 450 μm
● 8 μm Beryllium window in cap
(avoid visible light detection)
● Internal Zr-collimator (3.2 mm diam.)
● Moderate cooling by Peltier cooler
● Energy resolution: 133 Mn-Ka
● Pulse Reset Preamplifier
● 6 different Be-filters, 17 pinhole apertures
Energy Calibration (in-situ X-Ray Tube)

4. 2. Experimental Setup (cont‘d)
Lynx Digital Signal Analyzer (Canberra)
● control & readout via network PC
● oscilloscope function
● external trigger
● elimination of preamp reset pulses
● multispectral scaling (MSS) and
time-stamped list mode for time
resolved measurements
● stand-alone MCA operation
(via web-browser or mca-client )
as well as shot synchronized data
acquisition via C++ toolkit

5. 3. Tungsten dominated Plasmas with Te < 5 keV
● Typically, tungsten ion charge states
in the range W30+ … W50+
expected in plasma core [1,2,7]
● Coronal cooling rates [4] for tungsten
calculated with ADAS atomic data
package including model for
response function of SX Camera [4]

6. 3. Tungsten dominated Plasmas with Te < 5 keV (cont‘d)
Comparison of PHA data with data from SX Cameras (SXC) and from VUV spectroscopy
- Low-density L-mode plasma with RMP operation window -
● Te, ne & profiles unaffected by RMP-coils [3]...
● ... but large reduction of core radiation
& tungsten concentration (from VUV)
● SX PHA spectra normalized to response
function of SX cameras (SXC)
good agreement PHA – SXC !
● W concentration from modelling of SX radiation
with cooling rates somewhat lower than VUV data

7. 4. Dependence of Tungsten PHA Spectra on Te
Tungsten M-line radiation in plasmas with Te < 5 keV, thin Be-filter
● 3 clusters of W L-lines at Te > 1.5 keV, mainly from states W38+ … W49+ [2,5,6]
● lowest energy peak around 1.7 keV (6.8 Å) attributed to 4-3 transitions in W ,
disappears below Te < 1.5 keV (as highest peak due to 5-3 transitions)
● main peak around 2.15 keV (5.8 Å) shifts downwards with decreasing Te

8. 4. Dependence of Tungsten PHA Spectra on Te (cont’d)
Tungsten L-line radiation in plasmas with Te > 5 keV, thick Be-filter
ADAS modeled spectra
for EBIT data
● First observation of W L-lines in fusion plasma with Te = 12–18 keV, states up to W65+ !
● Progressive upward shift and broadening of W lines with increasing Te,
due to shifts of mean ionic charge (ADAS modelling [2,5])
● Tungsten L lines may be masked by Copper K-lines, no clear evidence from VUV

9. 5. Other Impurities, Impurity Density Analysis
● Ar contamination sometimes after
disruption mitigation by massive
gas puff. Also due to leaking
gas filled X-ray detector.
● Ar concentrations agree within factor 3
with values derived from Johann
spectrometer (discrepancy due to
different atomic data set and modeling ?)
● Ti events, presumably flakes from
NBI beamline
● Fe, Cr, Cu influx due to arcs on remote
in-vessel components (?)
● besides Fe K-lines also L-lines observed
(and/or Cu L) in low Te phases (Te < I keV)
● modeling of spectra with IONEQ [8]
using measured [9] and model profiles
for Te & ne yields impurity concentrations

10. 5. Other Impurities, Impurity Density Analysis (cont’d)

11. 6. Electron Temperature Analysis
Slope of continuous part of spectrum contains Te averaged
in the hot plasma core along the almost central line of sight

12. 6. Electron Temperature Analysis (cont’d)
Estimates of the central electron temperature
obtained from forward modelling of the emission

13. (DRift detector Array-based Gamma camera for Oncology)
7. Conclusions, Outlook
● PHA system with a SDD detector very sensitive for detecting low impurity concentrations
of medium- to high-Z impurities in the plasma core
● State of the art detector and electronics allows operation at high count rates (up to 500 kpcs),
and hence, time resolved spectroscopy with moderate time resolution (4 Hz typically)
● Soft X-ray PHA spectra are useful for cross calibration of various X-ray diagnostics
● Radiation from very high ionization stages of tungsten could be observed
the first time at ITER relevant electron temperatures
● Tests of SDD based advanced detectors including scintillator coupled
imaging detectors for hard X-rays have been started.
DRAGO:
(DRift detector Array-based Gamma camera for Oncology)
Array of 77 hexagonal SDD cells [10]

14. References
[1] R. Neu, et al. Plasma Phys. Control. Fusion 49(12B) B59 (2007)
[2] T. Pütterich, et al. Plasma Phys. Control. Fusion 50(8) (2008)
[3] W. Suttrop, this conference (2011)
[4] T. Pütterich, et al. Nucl. Fusion 50(2) (2010)
[5] C. Biedermann, et al. Phys. Scr. T (2009)
[6] R. Radtke, et al. J. Phys.: Conf. Ser. 58(1) 113 (2007)
[7] R. Dux, et al. Nucl. Fusion 51(5) (2011)
[8] A. Weller, et al. Modelling of soft X-ray emission from JET plasmas,
Report JET-IR(87)10 (1987) (unpublished)
[9] R. Fischer, et al. Fusion Science and Technology 58(2) (2010)
[10] C. Fiorini, et al. Nuclear Science, IEEE Transactions on 52(4) (2005)