Straw Characterization Based Upon 55 Fe Plateau

1. Straw Characterization Based Upon 55Fe Plateau Miguel A. Morales University of Puerto Rico at Mayaguez SIST Program – Fermilab

2. Outline • Introduction • Description of the project • Objectives and Motivations • Fundamental Processes • Experimental Setup • Results • Height of the Plateau • Edge Voltage • Gas Gain • Leaks • Conclusions

3. Introduction • Description of the project • Study of the lower edge of the plateau of the detector using an 55Fe source. • Objectives and Motivations • Find appropriate parameters with which we could measure the uniformity and quality of the straws in a detector. • Develop methods to be used during the detector’s assembly and installation in 2009.

4. 5.89 keV 55Fe source ~3.2 keV ~2.69 keV Photon (5.89 keV) Drifting electrons : : : : : : : : : : : : : : : : Primary electron cluster …. ~ 226 e- Straw Wire • Fundamental processes • A photon produced by the source enters the gas volume and is absorbed. • As a consequence of the absorption, two electrons are liberated by the atom. • Further electron-ion pairs are produced. • The electron cluster drifts toward the wire. • Avalanche multiplication occurs, increasing drastically the number of electrons.

5. Experimental Setup Detector’s Description • 48 straws • 3 closely packed layers of 16 straws • 4 mm diameter • Composition: • Outer layer: 25 μm Kapton film • Inner layer: 25 μm carbon-loaded Kapton film • 0.2μm Al film • 1 meter long • 25 μm Au-coated W wire • Ar/CO2 (80/20) flows through the straw volume

6. Experimental Setup Detector Description (cont.) • The source used was 55Fe. • x-ray energies = 5.89 keV • 25.5 cm from middle layer of straws • 5 positions along the straw (from electronics’ end) • 16.5cm 4. 66 cm • 35.5 cm 5. 90 cm • 52 cm • Flow rates • 0.4 scfh (standard cubic feet per hour) • 0.9 scfh

7. Straw Prototype Detector

8. Results • Parameterization of the plateau curve

9. Height of the Plateau • Beam distribution is uniform across the layers. • Good parameter to measure uniformity and efficiency. • Strong dependence with straw position in the module.

10. Edge Voltage • Good parameter to study gain variations across the length of the straw. • Strong dependence with the gain and the threshold of the system. • Values for the prototype ranged between 1090 and 1110 V.

11. Obtained from previous experiments on the Single Straw Prototype. Measures the gain needed by the signal to reach the threshold. Values ranges from 1800 to 2200. Gas Gain at Edge Voltage

12. Edge Voltage vs Source Position • Signals produced near the electronics' end • travel different distances, reaching the • electronics at different times.

13. For normal straws, δ=1 because the edge voltage should not depend on direction of gas flow. Because of leaks, the gain changes, increasing the edge voltage For leaky straws, δ < 1. Gas Leaks Gas flowing from electronics: Gas flowing toward electronics:

14. Gas Leaks • Leaky Straws are consistent.

15. Conclusions • Uniformity and Quality • Height of the plateau • Gain Variations • Edge Voltage • Range Found: (1090-1110) • Gas Leaks • Change direction of the gas flow

16. Acknowledgements • Alan Hahn • Penny Kasper • John Krider • Bill Pritchard • SIST Committee

17. Questions???