28
Advanced X-Ray
Detectors for Transmission Electron Microscopy--Photon Imaging, Inc., 19355
Business Center Drive, Suite 8, Northridge, CA
91344; 818-709-2468, www.photonimaginginc.com
Dr. Jan S. Iwanczyk, Principal
Investigator, iwanczyk@compuserve.com
Mr.
DOE Grant No. DE-FG02-03ER83873
Amount:
$750,000
In materials research, the current generation
of detectors used for Transmission Electron Microscopy (TEM) are Si[Li]
cryogenically cooled devices. Their
count rate is severely limited to about 3K/sec making two-dimensional elemental
mapping extremely time consuming. For
example, this low count rate makes it impossible to acquire elemental maps
simultaneously with near-real-time images, thereby impeding the analysis of
data. Furthermore, current detectors
are prone to radiation damage caused by high-energy backscattered electrons.
This project will develop silicon drift detector (SDD) technology and
produce a new type of detector that has a very low capacitance and can achieve
low noise at short shaping times. This
feature will allow the simultaneous attainment of very high-count rates and
excellent energy resolution, required for elemental mapping.
The SDD device is expected to yield electronic noise better than 10
electrons RMS (70 eV FWHM) at optimum peaking times of ~500
ns and posses an active area up to 0.5 cm2.
Also, the implanted contact technology used for SDDs should have better
radiation resistance than the Schottky-barrier type used with Si[Li] detectors.
Phase I developed a prototype detector
package that was inserted into a TEM at Argonne National Laboratory for testing.
The performance of the system has exceeded all measures of success.
Phase II will further optimize the detector structure through detailed
computer simulations and modeling. Optimized
devices will be constructed, and the improved detectors will be assembled into a
specialized spectrometric package for use in TEM instruments.