Silicon Detector Array (SIDAR)

Silicon Detector Array (SIDAR)
The Silicon Detector Array (SIDAR) is a collection of single-sided silicon strip detectors for experiments in nuclear astrophysics and nuclear physics.  It offers high granularity, excellent energy resolution, and good resolution in position, angle, and timing.  The array can be configured in a variety of arrangements within a dedicated target chamber with the limiting factors of geometry and the number of electronics channels that can be stored simultaneously.  We are currently limited to about 256 channels.  Detector signals are usually read from the p-type strips, however, it is also possible to read out just the n-type pad reducing the number of channels at the cost of resolution and position information.  Amplification is performed using 8-channel amplifiers/discriminators from Rutherford Appleton Laboratory where the gains are set using plug-in resistor chips and a common threshold per module.  Peak sensing 8-channel CAMAC ADCs originally developed by Silena are used to digitize the peak heights with the count rate limited to about 2 kHz.  We have also used faster VME ADCs from CAEN which allow for count rates up to about 7 kHz.

We have available a variety of geometry and thickness detectors all purchased from Micron Semiconductor.  The original system was modeled after the Louvain-Edinburgh Detector Array (LEDA) and was composed of YY1 design detectors.

YY1 detector


Eight of the YY1 detectors can be arranged in a flat annular array with sixteen 0.5-cm strips covering radii from 5 to 13 cm.  Six detectors can also be configured in a "lampshade" arrangement to cover a larger angular range.  The quantity and thicknesses of available YY1 detectors are listed below.

Thickness
Style
Quantity
65 micron
YY1
8r
100 micron
YY1
6
300 micron
YY1
6
500 micron
YY1
6
1000 micron
YY1
8


Other smaller annular detectors are also available including two S1-style 300 micron thick detectors with 4 quadrants of 16 rings subtending radii from 2.4 to 4.8 cm in 1.5 mm strips and one S2-style 300 micron thick detector with 48 rings subtending radii from 1.1 to 3.5 cm in 0.5 mm strips.  The S-style detectors are good complements to the YY1 detectors when detection of particles over most of the forward or backward hemispheres is required.

In addition to the annular detectors, we have several styles and thicknesses of rectangular 5cm X 5cm pad and strip detectors.  
5cm X 5cm detector

The strip detectors are divided into 16 strips (5cm X 0.3 cm), and some are position-sensitive where the position along the strip is determined via charge division with resolution ~ 1 mm.  The quantity and thicknesses that we have available are listed below.

Thickness
Style
Description
Channels/
Detector
Quantity
850-1000 microns
MSX25-1000
Pad
1
5 (1 on order)
300 microns
W(SS)-300
Strips
16
2
1000 microns
W(SS)-1000
Strips
16
2
65 microns
X1-65
Position-
Sensitive
32
4
140 microns
X1-140
Position-
Sensitive
32
5


The SIDAR array has been used for a variety of radioactive ion beam [1-10] and stable beam experiments [11-12].  As a result of the large solid angle coverage and segmentation of the array, it naturally lends itself to making kinematically-complete measurements such as the 1H(18F,alpha)15O measurement pictured below.


18F(p,alpha)15O experiment
From left to right:  The experimental setup for the 1H(18F,alpha)15O measurement is shown.  The 18F/18O beam impinged on a CH2 target.15O ions and alpha particles were detected in the SIDAR array configured in lampshade mode.  The middle picture shows by plotting the a energy vs. the heavy recoil energy, the events of interest were clearly identified.  The right picture shows the excitation functions measured for 1H(18F,alpha)15O and 1H(18F,p)18F by stepping the beam energy through a resonance of interest.



The range of thicknesses of detectors makes particle identification possible while still simultaneously measuring the energy and angular distributions of reaction products.  A typical particle identification spectrum measured in a study of the 2H(18F,n)19Ne* reaction is shown below.



18f(d,n)

The experimental setup for study of the 2H(18F,n)19Ne* reaction is shown.  A 18F beam was used to bombard a CD2 target.  15O ions and alpha particles from the break up of the recoil 19Ne atoms were detected in position-sensitive particle telescopes.  The picture on the right shows the particle identification observed in the forward angle telescope.  The separation of F, O, N, C, and He isotopes is clear.



In addition to the SIDAR array, we are currently working on a next generation silicon array (ORRUBA) optimized for detection of charged particles near 90 degrees in the laboratory.

The SIDAR array was developed by the RIBENS collaboration involving researchers from multiple institutions including ORNL, Tennessee Technological University, Rutgers University, Yale University, University of North Carolina at Chapel Hill, University of Edinburgh, and Colorado School of Mines.


References

  1. First study of the level structure of the r-process nucleus 83Ge, J. S. Thomas et al., Phys. Rev. C 71, 021302(R) (2005).
  2. New constraints on the 18F(p,alpha)15O rate in novae from the (d,p) reaction, R. L. Kozub et al., Phys. Rev. C 71, 032801(R) (2005).
  3. Elastic scattering of the proton drip-line nucleus 17F, J. C. Blackmon et al., Phys. Rev. C 72, 034606 (2005).
  4. The 17F(p,gamma)18Ne direct capture cross section, J. C. Blackmon et al., Nucl. Phys. A 746, 365c (2004).
  5. Search for astrophysically important 19Ne levels with a thick-target 18F(p,p)18F Measurement, D. W. Bardayan et al., Phys. Rev. C 70, 015804 (2004).
  6. The 14O(alpha,p)17F reaction rate, J. C. Blackmon et al., Nucl. Phys. A 718, 127c (2003).
  7. Strength of the 18F(p,alpha)15O resonance at 330 keV, D. W. Bardayan et al., Phys. Rev. Lett. 89, 262501 (2002).
  8. Destruction of 18F via 18F(p,alpha)15O burning through the Ec.m. = 665 keV resonance, D. W. Bardayan et al., Phys. Rev. C 63, 065802 (2001).
  9. Kinematically complete measurement of the 1H(18F,p)18F excitation function for the astrophysically-important 7.08-MeV state in 19Ne, D. W. Bardayan et al., Phys. Rev. C 62, 042802(R) (2000).
  10. Observation of the astrophysically-important 3+ state in 18Ne via elastic scattering of a radioactive 17F beam from 1H, D. W. Bardayan et al., Phys. Rev. Lett. 83, 45 (1999).
  11. Study of the 124Sn(d,p) reaction in inverse kinematics close to the Coulomb barrier, K. L. Jones et al., Phys. Rev. C 70, 067602 (2004).
  12. Astrophysically important 26Si states studied with the 28Si(p,t)26Si reaction, D. W. Bardayan et al., Phys. Rev. C 65, 032801(R) (2002).

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This file last modified Tuesday September 25, 2007