1. The LH2 target has to be in the para-hydrogen state. At room temperature H2 is 75% ortho and 25% para. To catalyze the conversion between ortho and para states requires magnetic material (such as rust Fe-O) with large surface area. The energy difference between these two states is about the same as the heat of vaporization per molecule of hydrogen. The experiment requires OPCs to reduce the heat load to the cryo-refrigerators and to convert LH2 effectively to the para-hydrogen state. We an external and internal OPCs. LH2 Target - External ortho-para converter

3. At LANSCE we used precooler/OPC Cave roof

4. Pneumatic valve interlocked to H2 sensor

6. Target Interlock System as it was at LANSCE ParameterWarningAlarm Gas panel H2sxBuzzer, local flashing red light Cave H2 sxBuzzer, local flashing red light+ cave power off, ER2 evacuation alarm, fast target vent Cave O2NoIts own buzzer in cave + H2 buzzer, local flashing red light He partial pressure in vacuum xBuzzer, local flashing red light Isolation vacuum pressure xBuzzer, local flashing red light + close PV100, PV204, PV303 LH2 pressurex He channel flowx He channel pressurex Warning: buzzer and blinking read light in the H2 monitor pannel and on target operator desk.

7. LANSCE LH2 Target Interlock Diagram

8. LH2 Target Operating procedures Other Target Safety Related Issues Target operators -Senior and Junior Operators - are OJTed. At LANSCE we had an approved training program. –Senior Operator for the NPDGamma LH2 Target Operations Course #38145 –Junior Operator for the NPDGamma LH2 Target Operations Course #38146 1.The NPDGAmma Liquid Hydrogen Target User’s Guide V 1.12 Sep-4, 2006. Target User’s Guide includes a number of step-by-step procedures for different target operations. 2. Procedures for Abnormal LH2 Target Situations, July -13, 2006

9. LH2 Target -Vent isolation box