|
Photon Detector Categories Timing with
Germanium (HPGe) Coaxial Detectors
The timing performance of a coaxial detector defines its ability to
distinguish between two events closely spaced in time. Timing performance depends greatly
on proper electronic setup. Table 5 shows some typical timing results measured with ORTEC
detectors. The timing performance of a 61% GAMMA-X detector (with a Model 583
Constant-Fraction Discriminator threshold set at 50 keV and the energy range selected with
a Model 551 Timing Single-Channel Analyzer) is as follows:
| At E > 100 keV |
FWHM = 5.5 ns |
|
At E = 1.33 MeV (±50 keV) |
FWHM = 3.7 ns
FW.1M = 8.9 ns |
Results obtained with large GAMMA-X detectors are shown in Table 6.
Table 5. Typical Timing Results Measured
with ORTEC’s Coaxial Detectors. |
Detector
System |
Detector
Type |
Efficiency
(%) |
Optimum
Delay
(ns) |
Measure |
Timing Resolution (ns) |
| Mean Energy (keV) Using 22Na |
Mean Energy (keV) Using 60Co |
| 150 |
250 |
350 |
511 |
511 |
750 |
950 |
1170 |
1330 |
| 1 |
HPGe-P |
11.0 |
24 |
FWHM
FW.1M |
9.2
– |
6.7
45.3 |
5.8
22.2 |
4.0
9.9 |
3.9
10.2 |
3.0
8.4 |
2.6
7.5 |
2.0
5.6 |
1.7
5.1 |
| 2 |
HPGe-N |
19.8 |
23 |
FWHM
FW.1M |
12.5
84.0 |
8.6
33.0 |
7.0
18.1 |
4.5
10.2 |
4.9
11.8 |
3.7
8.6 |
3.1
7.7 |
2.2
5.5 |
2.0
4.9 |
| 3 |
HPGe-P |
28.0 |
34 |
FWHM
FW.1M |
11.3
– |
8.8
55.8 |
7.7
27.1 |
5.6
12.8 |
6.2
13.4 |
5.7
12.3 |
4.0
11.8 |
3.6
9.8 |
3.4
9.0 |
Table 6. Timing Data Obtained on Three High
Efficiency
GAMMA-X Detectors Included in the EUROGAM Array
(P. Nolan, et al., Internal Daresbury Report – July 1991). |
|
Detector |
Efficiency (%) |
E (keV) |
FWHM (nsec) |
|
A |
69.2 |
50–1332
1332
779
344
122 |
5.8
4.3
6.8
9.0
19.0 |
|
B |
80.2 |
50–1332
1332
779
344
122 |
9.2
6.7
8.7
13.3
18.1 |
|
C |
70.2 |
50–1332
1332
779
344
122 |
7.2
4.7
6.0
10.6
22.2 |
|
