High Resolution Array

HiRA is a collaborative project between Indiana University (deSouza,Viola), Michigan State University (Lynch,Tsang), and Washington University (Charity,Sobotka). It was funded by the National Science Foundation's Major Research Instrumentation initiative in 1999 to develop a large solid angle (high efficiency) array of Si-Si-CsI(Tl) telescopes with good angular and energy resolution for radioactive beam studies. The principal physics objectives of HiRA are elastic and inelastic scattering measurements with radioactive beams (astrophysically important measurements), resonance spectroscopy, isospin dependence of the nuclear equation-of-state, and nuclear reaction dynamics studies. In designing and constructing HiRA we build upon our experience in the design, construction, and performance of the recently completed array LASSA. Recently we have been joined by A. Moroni, INFN Milan on this project.

Update: As of Aug. 1, 2003 we have received, tested, and accepted 12 of the 1.5 mm Silicons. We have received 6 DE detectors which are undergoing testing.

One possible configuration of the 20 telescopes which constitute HiRA
Responsibilities in the HiRA project  
Silicon design and testing Indiana University desouza@indiana.edu
Electronic (ASIC) design and fabrication Washington University lgs@wuchem.wustl.edu
Mechanical design  Michigan State University lynch@nscl.msu.edu
Mechanical design INFN, Milan arialdo.moroni@mi.infn.it
Project management Michigan State University lynch@nscl.msu.edu


1. Rough parameters for HiRA

HiRA will consist of 20 telescopes based upon a Si-Si-CsI(Tl) stack for identifying charged particles in Z and A by the DE-E technique. Each telescope will be constructed from a 65 micron strip Si(IP) detector backed by a 1.5 mm silicon strip detector. The 65 micron detector will be single sided (32 strips on the junction (front) side only), while the 1.5 mm detector will be striped in 32 strips on the junction side with 32 orthogonal strips on the ohmic (rear) surface. Thus the 1.5 mm will provide two-dimensional position information. The detectors will have a 2 mm pitch with a 25 or 40 micron interstrip gap (junction and ohmic surfaces respectively).

2. Silicon design

In contrast to our previous array LASSA, for HiRA we will be designing a new silicon detector in conjunction with Micron Semiconductor Ltd. This need for a new design is driven by the unavailability of the desired pitch in an existing design of the necessary size. Our present design has the following features.

3. Electronic development

HiRa will consist of 1920 channels of Si electronics and 80 channels of CsI(Tl) electronics for which good resolution (< 40 keV for a 6 MeV alpha in the Si) is essential. This large number of channels mandates a new approach in our electronic design. We have opted to pursue the development of an ASIC (Application Specific Integrated Circuit) in collaboration with George Engle (University of Illinois, Edwardsville). The ASIC will contain (for either 8 or 16 indepedent channels) a high quality charge sensitive preamp, shaping amplifier, timing filter amplifier, discriminator, and time-to-charge convertor. Due to the sparse nature of the data in an event recorded by the array, the digital and analog streams will be multiplexed out of the chip. A token passing scheme will allow daisy chaining multiple ASICs.

5. Photographs of HIRA Si being tested

A HIRA Si upon arrival in the new shipping containers designed at Micron in July 2003.
The pumping station in Rm 03 used to test the HIRA Silicons.
The electonics and Data Acquisition setup used to test the HIRA Silicons.
A HIRA Si in the vacuum chamber ready to be tested with an alpha source.
Another perspective of a HIRA Si undergoing testing with an alpha source.

Ready for experiments

HIRA ready for its first experiment in the S800 scattering chamber at MSU.
July 2005
HIRA ready for its first experiment in the S800 scattering chamber at MSU.
July 2005
Together with the microchannel plate (left side of photo) and the S800 spectrometer, HIRA is ready to measure the breakup of 74Br.
July 14th, 2005