Summer Work

• Noise Measurements of Silicon Microstrip Detectors
  
• Testing of Silicon Strip Detectors with 106Ru and Lead
  
• X-Ray Imaging
  
• Analog Chip Testing
  
• CMOS Transistor Matching
  
• Hybrid Construction and Testing
  
• Data Transmission Simulation
  
• World Wide Web
  
• Cerenkov Counter Testing
  
• X-Ray Research
  
• Detector Characterization
  

In an experiment, the signal caused by a particle passing through the detector can easily be affected by noise generated by the detector or the electronics used to read out the signal. In this project we measure the noise of silicon microstrip detectors for different strip lengths and resistances.

For more info, see this page directly.

A crucial point for the usefulness of operating silicon detectors at future colliders is how they will behave in a high radiation environment. The radiation creates acceptor states in the substrate and a primarily n-type doped substrate changes into an p-type substrate for high irradiation doses, called type inversion. Later we may try using an LED light, a more direct way which penatrates only a few tenths of a micrometer in silicon before it is absorbed. Therefore, the created electron hole pairs are close to the surface of the detector, comparing the penetration depth and detector thickness. These pairs are only collected if the depletion region extends close to the surface. The aim of this experiment is to measure the detector's response using beta paticles from a Ruthenium source, and to find out how the response depends on the irradiation.

For more info, see this page directly.

X-Ray Imaging

In order to pin-point where a particle (in our case an x-ray) comes through the detector, we can look for coincidence in space between the two sides of the detector. In this project we first measure the energy spectrum of various targets placed in the x-ray beam. We also set up the system so that we can analyze the coincidence of signals and therefore pick out the true signals from the noise. We use this to do imaging of differect size slits placed in front of the x-ray beam. We use two detectors to get a two dimentional (i.e.. x and y direction) mapping of the position of the particle.

For more info, see this page directly.

For more info, see this page directly.

Transistors are used for low power analog readout for the detectors. We are using chips with differential pairs of CMOS transistors. Each chip is given the same fixed drain, source, snd substrate voltage and the drain currents are measured for different gate voltages. From this, the transconductance (1/R) and the current mismatch, the difference between the two drain current, is obtained. We wrote the software used to allow the computer to "talk" to the parameter analyzer, which takes the data during the tests. We will also be irradiating the transistors with gamma rays, and retesting and reanalyzing the data.

For more info, see this page directly.

We work on two of the current SCIPP projects in particular -- Zeus and ATLAS . Zeus is nearing its final stages, and for this project we focus on testing and characterization of completed assemblies, culminating in shipping of the detectors to Germany in late July. The ATLAS project is in its early stages, and for this project we work toward an upcoming beam test. For this, we are testing the continuity on Kapton hybrids, working on the atlas_daq code, constructing and testing the Cable interface board, and other tasks needed for constructing and testing for the project.

For more info, see this page directly.

The ATLAS collaboration working on a silicon tracking detector has proposed a protocol for serial data transmission of commands from the detector to the data acquisition system and also for transmission of commands from the control system to the on-detector electronics. While the proponents of the protocol believe thay have developed an algorithm for encoding information and marking information boundaries which can be correctly interpreted by the receiving circuit, we simulate the transmitting and receiving algorithms to verify their correctness before the integrated circuits are built. Also, the proposal makes claims about the protocol's tolerance to transmission errors. We test this by injecting errors into the simulated data and observing the algorithm's ability to cope with the errors.

For more info, see this page directly.

We are setting up a World Wide Web site for SCIPP, both to present activity happening here for the curious and to share information between active people of current experiments. We are learning how to write in HTML, how to scan pictures using PhotoShop, and how to put it all together to create a real SCIPP site.

For more info, see this page directly.

We are currently setting up a new lab to do some maintenance/upgrade work in a Cerenkov detector which is used to detect Compton-scattered electrons from the high energy electron beam at the Stanford Linear Accelerator Center. Using Labview, we set up a data acquisition system which will be used to test and characterize photomultiplier tubes to be used in the Cerenkov detector. We also are developing and testing a temperature control system for the accelerator, allowing us to insulated the detector from the high (>45 degrees C) ambiant temperature in the Stanford accelerator tunnel. Finally, we do R&D on a laser/light-fiber calibration system to accurately measure phototube response linearity and to monitor phototube gain drifts while the detector is in place in the accelerator tunnel.

For more info, see this page directly.

Two major causes of death among adults in industrialized nations are atherosclerosis (hardening of the arteries) and lung cancer. Both of these ailments are treatable if detected early in the progress of the disease, but are often fatal if not. Currently, there are no available non-invasive diagnostic procedures, but we have developed a diagnostic method that shows great promise in the diagnosis of these two diseases. Both involve the use of synchrotron radiation, a highly collimated beam of x-rays emerging from electron storage rings that can be focused and rendered monochromatic by careful choice of optical components. In this project, we test a new concept in x-ray monochromators that utilize the concept of Bragg reflection from perfect crystals of silicon to achieve highly collimated, intense, monochromatic beams. Soon some human trials will be conducted at Brookhaven National Laboratories in New York.

For more info, see this page directly.

This project was begun last year as one of a number of studies connected with a proposal to NASA to use silicon strip detectors in a next-generation orbiting gamma-ray pair-conversion telescope. The detectors will have wide pitch (300 microns) and narrow strips (30 microns). The use of narrow strips in the detectors would result in a considerable savings in electrical power. In such a device the detectors would be placed between thin sheets of lead, which would serve to convert incident gamma rays into electron-positron pairs. The silicon detectors would then measure the trajectories of the electrons and positrons to reconstruct the direction of the incident photon. We are concerned that these types of detectors might have poor charge collection from tracks which pass midway between the strips. We are making more measurements to verify this possible result. We have been getting inconsistent results, varying from one day to another when using a fast amplifier. So far the use of a slow amplifier has never shown loss of signal in the interstrip region. Further data is being taken to investigate these results.

For more info, see this page directly.