D-Zero Solenoid Quench Investigation: Observations, Tests, and Commentary Fall 2004 - Spring 2005
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
The D-Zero solenoid operated reliably at 4750 Amperes (2 Tesla) from its manufacture in 1997 through August of 2004. During the period of August thru November 2004, the solenoid was warmed to room temperature for maintenance work and then re-cooled. After re-cooling, the Solenoid was not able to reach full current. An investigation began to understand the cause and ultimately how to limit or prevent further degradation in performance. A stable operating current of 4550 Amperes was chosen to allow physics analysis to continue at reduced magnetic field strength (1.92 Tesla). The investigation revealed clear evidence of an excessively resistive solder joint in a conductor transition joint in the inner layer winding of the two layer solenoid coil. The resistive joint generates Ohmic heating and raises the local superconductor temperature to critical temperature at the magnetic field strength and current of about 4650 Amperes. This is believed to be the primary cause of the degradation in performance. Temperature sensors located above the resistive joint area see a temperature increase from the resistive solder joint. Historical trending of these sensors at 0 current and full current gives a picture of the joint worsening with time. Coupling the trend with operational history leads one to believe that the joint degradation is connected with thermal cycles of the solenoid. We believe that preventing thermal cycling will prevent future degradation/increased resistance in the joint. Another interpretation of the data (although less compelling) is that the degradation could be time dependent or energization cycles. Although this conclusion is not as strong, we now also limit power cycles and field reversals. Procedures are in place to prevent warming the solenoid coil. Increased resolution temperature monitoring of the resistive joint has been in place since December 2004 and no increase in temperature elevation has been detected. A resistance monitoring system is being developed that should yield electrical resistance measurements of the degraded joint itself. A helium refrigerator upgrade consisting of a cold compressor is in progress. It will reduce the liquid helium coolant temperature for the solenoid and also the conductor winding to gain additional operating margin.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1460795
- Report Number(s):
- FERMILAB-D0-EN-576; 1085602; TRN: US1901705
- Country of Publication:
- United States
- Language:
- English
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