Dualaxis Duo Lateral Position Sensitive Detectors Robin Dienhoffer
Dual-axis, Duo Lateral Position Sensitive Detectors Robin Dienhoffer State University of New York at Oswego Advisor: Dr. Sherry Yennello Cyclotron Institute, Texas A&M University
Outline Particle Detectors ¢ Silicon Detectors ¢ Position Sensitive Detectors now ¢ New Position Sensitive Detector ¢
Particle Detectors ¢ Materials and forms used Solid, liquid & gas l Various elements l • Germanium, Cesium iodide, silicon, plastic… ¢ Various Attributes l Stopping power • ΔE vs. E plots Energy and position resolution l Cost l Ease of handling l ¢ Combining Detectors
Silicon Detectors Not overly sensitive to humidity and operates well at room temperatures ¢ Delicate, but not impossible to handle ¢ Still expensive, but becoming more widely used ¢ Band Gap ¢
Band Gap ¢ Energy difference between valance band conduction band l l ¢ ¢ Conduction Band Silicon is a good material to detect the particles that we work with To get to the conduction band, approximately 2. 8 e. V are needed To get a readable charge, electrons must be excited enough to “jump” to the conduction band This charge is then collected by the charge collection strips to be converted to signals Band Gap Valance Band
What are PSDs? PSD stands for Position Sensitive Detector ¢ Collects deposited charge in such a way that the position of the particle can be determined ¢ This will allow us a more thorough understanding of the underlying reaction mechanism that produced the charged particles ¢
FAUST The Forward Array Using Silicon Technology ¢ Currently uses discrete detectors ¢ Position information restricted to which detector was hit l Hoping to upgrade to PSDs, giving better position resolution l
Some PSDs in Use ¢ Pixilated Detectors Strip detectors that use separated pads of Silicon to detect where the particles hit l The number of channels of electronics limit the feasibility of this option l ¢ Resistive Detectors Dual-axis l Tetra-lateral l DADL l
Dual-axis ¢ ¢ Signal pulled from the edge centers This results in circular pulling that must be adjusted through correcting algorithms
Dual-axis Tetra Lateral ¢ ¢ Dual-axis Tetra lateral detector collects charge at all four of the corners on one face of the detector This causes a pincushion effect which must, again, be accounted for using correction algorithm
Four Corner PSD – Dr. Tribble’s Group Resistive sheet of Si on front and a non-resistive sheet on the back ¢ resistive strips on front edges correct pincushion effect ¢ Five signals- four on front and one on back (total energy) ¢
Dual-axis, Duo Lateral ¢ Dual-axis, duo lateral PSDs collect charge in a way which give position from both the front (horizontally) and the back (vertically). This method will lead to much less distortion than in previous models.
Front 1 F 2 Back 2 Guide wires for charge Charge collecting strips F 1 Back 1 Front 2
Detecting Location Edge 1 Edge 2 L 1 L 1 Guide Wires L 1 Charge Collection L 2 When L 1 = L 2, both edges receive the equal charge, or Q 1 = Q 2 When L 1 > L 2, Edge 1 receives less charge, or Q 1 < Q 2 When L 1 < L 2, Edge 1 receives more charge, or Q 1 > Q 2
Another Perspective V 1 /// Vo Vo = V 1 + V 2 /// V 2
Settings Found that biasing the front to 40. 0 volts and the back guard ring to 5. 0 volts is the most effective to get a clear energy spectra and position graph ¢ Shaping time of 1 μs or 3 μs gives both good energy and position resolution ¢
228 Th Energy Spectra 5. 686 6. 051 6. 288 6. 778 5. 432 8. 784
228 Th Position Graph
Beam Time: Ag + nat. Au ΔE-E Graph Triton Deuteron Z=3 Z=2 Z=1 Proton
Beam Time: Ag + nat. Au Position Graph
Hole Ratios Mask Measured 3 mm 250 Chan. 2. 5 mm 200 Chan. 1. 5 mm 125 Chan. Red Green = 1. 20, 1. 25 Red Blue = 0. 50, 0. 50 Green Blue = 1. 67, 1. 60
Future Use This PSD design is currently being optimized for the future FAUST upgrade ¢ Micron Semiconductor is offering this detector to the scientific community at large ¢
Acknowledgements Dr. Sherry Yennello ¢ SJY Group ¢ REU Program ¢ NSF, Grant _____ ¢ ¢ ¢ Robert A. Welch Foundation, Grant A 1266 DOE, Grant DE-FG 03 -93 ER 40773.
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