1. 11/07/20071 Hardware Commissioning Forum: DFBs R. Rabehl AT-ACR

2. 11/07/20072 DFB Topics Sector 7-8 DFB Commissioning Results Issues Chimney condensation Level gauges Lead flow valves Future DFB commissioning

3. 11/07/20073 Sector 7-8 DFB Commissioning Results DFBs have been validated in all modes: 70 K standby, 50 K nominal, nominal ramping, flattop, sawtooth ramping. Formal documentation in progress.

4. 11/07/20074 DFB Chimney Condensation 13 kA chimneys 600 A chimneys 6 kA chimneys 120 A chimneys Conducting pad, atmospheric/active heater, dry air plastic bag, … Several possible solutions still requiring final validation.

5. 11/07/20075 DFB Level Gauges Calibration Sector 7-8 required in-situ calibration of all level gauges. In Sector 4-5, each DFB service chimney will have one pre- calibrated 150 mm level gauge (for level control) and one non- calibrated 400 mm level gauge (for monitoring). Normal operating setpoint for the calibrated 150 mm gauge will be at 50%. 400 mm gauge can be cross-calibrated against the 150 mm gauge. 150 mm gauge will be too short to see features such as the chimney dished head and the pigtail tube – the 400 mm gauge will need to be used for this.

6. 11/07/20076 DFB Level Gauges DFB level gauges seem to be affected by the LHe supply, giving a false high reading. As a result almost all Sector 7-8 DFB’s use a lead chimney LT as the process variable for liquid level control, but all Sector 4-5 DFB’s have LT’s in the service chimney only. Using a shorter gauge for level control should reduce this effect by moving the gauge away from the LHe fill tube. Level gauges will be enclosed to shield them from the LHe supply.

7. 11/07/20077 DFB Level Gauges He in/out Protective box Courtesy A. Perin

8. 11/07/20078 DFB Level Gauges Installed SC wire liquid level gauges provide inputs for the Cryo Start and Cryo Maintain conditions – they are not meant to protect equipment. A point level sensor will be installed in each DFB to provide an equipment protection interlock. The type of sensor to be used is under consideration.

9. 11/07/20079 DFB Lead Flow Valves During powering of DFBAs, flow valves of some non- powered leads appear to open more to maintain 50 K at the HTS. Electromagnetic interference with the temperature sensor is unlikely. Electromagnetic interference with the lead flow valve coil is possible. A change is gas temperature supplied to the leads is also possible as more gas is taken from Header D. On the Sector 7-8 DFBs, it is difficult to diagnose lead flow valve behavior. No position feedback from the lead flow valves. Virtual flowmeter calculation is generally not accurate and, in this case, not useful because it is based on requested valve position instead actual valve position.

10. 11/07/200710 DFB Lead Flow Valves Operationally this behavior is not a problem, but it would be interesting to understand. A few Sector 4-5 DFB chimneys will be equipped with mass flowmeters for current lead flow characterization. These will be useful for verifying the behavior of the flow valves during powering. A lead flow valve control test program to investigate lead gas supply (i.e., Header D) temperature and electromagnetic effects should be considered.

11. 11/07/200711 Future DFB Commissioning Analysis of DFB data and release of DFBs to HCC for powering will remain the responsibility of the CPP. ACR is re-organizing the DFB commissioning effort. R. Rabehl is leaving at the end of September. The next U.S. collaborator (C. Darve) will arrive in early September and will be occupied with the inner triplet and DFBX but should be able to contribute to general DFB commissioning, as well.

12. 11/07/200712 Summary All Sector 7-8 DFB’s were successfully commissioned. Issues identified and actions for Sector 4-5 Chimney condensation Long-term solutions have been chosen but remain to be validated. Liquid level Each DFB will have one pre-calibrated level sensor. Enclosure of sensors should shield them from the LHe supply (to be validated). Point level sensors for buswork protection will be integrated. Lead flow valve behavior Not an operational problem but interesting. Remains an open issue, to be resolved with mass flowmeters and additional tests. Commissioning effort ACR is reorganizing the DFB commissioning effort; the U.S. collaboration will continue to contribute.