Position-Sensitive Si(Li) Transmission Detectors for the EXL-Experiments at GSI-Darmstadt

D. Protić, T. Krings, S. Niessen, Forschungszentrum Jülich, Institut für Kernphysik (IKP), Jülich, Germany

P. Egelhof, Gesellschaft für Schwerionenforschung (GSI), Darmstadt, Germany

E. C. Pollacco, CEA Saclay, France

~ 6.5 mm thick

the same structure as for the Si(Li) detectors for the MUST2-setup

effective thickness below 5 m

without position-sensitive structure

design is identical to the MUST2-design

all components have to be UHV-compatible

T = 273 K

EXL-1 EXL-2

6.5 mm thick 6.4 mm thick

p+-contact is structured

Li-diffused contact has to be thinned

• transmission type Si(Li) detector

A large target-recoil detector will be constructed for the future EXL-experiments (EXotic nuclei studied in Light-ion induced reactions) at the NESR storage ring of the future FAIR project at GSI-Darmstadt [1]. As a part of the recoil detector, position-sensitive Si(Li) transmission detectors (5 to 9 mm thick) are intended for construction of E-E charged-particle telescopes. Si(Li) detectors of transmission type has been an important aspect concerning the total-energy measurement for target recoils transversing the silicon E-E telescopes and stopped in inorganic scintillators placed behind the telescopes.

Two ~7 mm thick Si(Li) transmission detectors equipped with 8 pads on the implanted p+-contact have being prepared for the test measurements at ESR (GSI-Darmstadt). To relieve the efforts for the first experiments a telescope configuration and position-sensitive structure very similar to that of the MUST2 experiment (SACLAY, ORSAY and GANIL) will be applied [2], but with UHV-capable components. Results of the test measurements in the laboratory are presented.

Abstract

References

[1] www.gsi.de

[2] E. C. Pollacco et al., to be published in Nucl. Instr. Meth.

[3] D. Protić and T. Krings, “Development of transmission Si(Li) detectors”, IEEE Trans. Nucl. Sci., vol. 50, pp. 1008-1012, August 2003

MUST2-Si(Li) setup and modifications for the EXL-Si(Li) setup

Si(Li) detector prototype for test measurements

MACOR-blocks

HV-board (ceramic)

to replaceceramic boards

MUST2-Si(Li) setup

MUST2-Si(Li) setup

PCBs out of FR4

Schematic view of the Si(Li) transmission detector

thinned Li-diffused n-contact covered with evaporated aluminum layer

(effective thickness [3]: < 5 m)

boron-implanted p+-contact covered with evaporated aluminum layer

(thickness: < 1m)

Al-bonded wires

~200 m wide connecting strips

8 position elements (pads) are separated by ~60 m wide and ~15 m deep plasma etched (SF6-

plasma) grooves

3 to 5 mm wide guard-ring

Li-compensated region (intrinsic zone)

Conclusion and outlook

• the manufacture of the two detectors will be completed within the next weeks. The Li-diffused contact of the Si(Li) detector EXL-1 will be thinned and the p+-contact of the Si(Li) detector EXL-2 will receive the position-sensitive structure.

• UHV-capable components of the detector holder have been already finished

• test measurements in UHV environment will be performed inside the ESR-ring at GSI-Darmstadt

Si(Li) detector EXL-1 in the UHV-compatible housing

p+-contact

ceramic board

Li-diffused contact(not yet thinned)

(structured with 8 pads)

(to contact the 8 pads)

HV ceramic board

MACOR blocks

Specifications: Momentary status:

• 8 pads on the boron-implanted contact

• thin Li-diffused contact

• operating bias:

• energy resolution [FWHM] for 5.8 MeV -particles:

• reverse current / pad:

• resistance pad - neighbourhood:

• housing / frame:

700 V

< 50 keV

< 250 nA

> 1 M

p+-contact is still without position-sentive structure

~ 3 m „thick“ Li-diffused contact

see: Results of the first laboratory measurements

the photolithography for performing the position-

sensitive structure on the p+-contact is started up

Results of the first laboratory measurements

EXL-1

EXL-2

operating bias: +700 V 298 K 283 K

• energy resolution [FWHM] per pad for 5.8 MeV -particles

26-41 keV 25-30 keV 23-25 keV

• reverse current per pad 110-200 nA 30-60 nA 15-31 nA

• resistance pad - neighbourhood > 1 M > 1 M > 1 M

• reverse current (total) 20 A 6.0 A 3.1 A

275 K

• energy resolution [FWHM] per pad for pulser line

15-29 keV 13-20 keV 11-13 keV

@ 273 K

1000 V 0.6 m 0.8 m

700 V 2.3 m 3.4 m

800 V 1.5 m 2.2 m

600 V 4.2 m 5.0 m

@ 298 K

effective thickness of the Li-diffused contact [3]determined with the help of -particles

ope

ratin

g b

ias

(n-contact)

(p+-contact)to replace by UHV-

capable parts

VESPEL-blocks

to replace

to replace

IEEE Nuclear Science Symposium, 29.10. – 4.11.2006, San Diego, USAContact: d.protic@fz-juelich.de, t.krings@fz-juelich.de, p.egelhof@gsi.de

test measurements(energy resolution, reverse

current, inter pad resistance) are being performed

54 mm

48 mm

~ 6.5 mm

Ø 102 mm

Ø 92 mm

for the EXL collaboration