Dual-axis, Duo LateralPosition 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 & gasVarious elements

• Germanium, Cesium iodide, silicon, plastic… Various Attributes

Stopping power• ΔE vs. E plots

Energy and position resolutionCostEase of handling

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 and conduction band Silicon is a good material to detect the

particles that we work with To get to the conduction band,

approximately 2.8 eV 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

Valance Band

Conduction Band

Band Gap

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 detectorsPosition information

restricted to which detector was hit

Hoping to upgrade to PSDs, giving better position resolution

Some PSDs in Use

Pixilated DetectorsStrip detectors that use separated pads of

Silicon to detect where the particles hitThe number of channels of electronics limit

the feasibility of this option Resistive Detectors

Dual-axisTetra-lateralDADL

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 pin-cushion 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.

F1

F2

B1

B2

Guide wires for

charge

Front 1 Back 2

Front 2Back 1

Charge collecting strips

Detecting Location

Charge Collection

Guide Wires

L1 L2

L2L1

L2L1

Edge 1 Edge 2

When L1 = L2, both edges receive the equal charge, or Q1 = Q2When L1 > L2, Edge 1 receives less charge, or Q1 < Q2When L1 < L2, Edge 1 receives more charge, or Q1 > Q2

/\/\/\ /\/\/\ /\/\/\VoV1 V2

Vo = V1 + V2

Another Perspective

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

228Th Energy Spectra

5.432

5.686

6.051

6.288

6.778

8.784

228Th Position Graph

Beam Time: Ag + natAuΔE-E Graph

Z = 1

Z = 2

Z = 3 Proton

Deuteron

Triton

Beam Time: Ag + natAuPosition Graph

Hole Ratios

Mask Measured

3 mm 250 Chan.

2.5 mm 200 Chan.

1.5 mm 125 Chan.

Red = 1.20, 1.25 Green

Red = 0.50, 0.50Blue

Green = 1.67, 1.60 Blue

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-FG03-93ER40773.