View source for Cryogenic Target Shift

== The Cryogenic Target ==

The Hall D cryogenic target consists of a tapered kapton target cell of 29.9 cm length, 2 cm diameter, a vacuum chamber, a pulse tube refrigerator, a compressor and its water cooling system, a gas manifold and panel, the electronic controls (PLC logic), a support cart and safety storage tanks. The figure below shows some of its main components.

[[File: target_fig.png]]

The cell can be filled with liquid H2 (physics run) or gas H2 (empty run).  It has a 130 um kapton wall and 75 um entrance and exit kapton windows. 

When filled with LH2, the operating pressure and temperature are P=18 psia and T=17K.

== Routine Operation ==

There are 3 routine operations:

* '''Empty target'''. Refrigerator is turned on and cell is cooled to temperature for cold H2 gas.

* '''Fill target with LH2'''. Refrigerator is turned on and cell is cooled to temperature for liquid H2.

* '''Turn off'''. Turns off refrigerator and lets the target warm up.

To turn on the target, use ''Empty'' or ''Fill'' buttons. It takes about 6h to cool the target from room temperature. To turn the target off use ''Turn off'' button.

Operation manual for the target can be found [https://halldweb.jlab.org/DocDB/0026/002682/001/Operation_HallD_Cryotarget_Rev1.pdf here].

<!--'''Do not change the target status without calling first an expert.'''-->

== Interlocks ==

Safety interlocks protect the target if the temperature decreases below 16K or the pressure decreases 16 psia.

If such event happens or if the target warms up, the target should not be damaged. However, beam time will be lost. '''Call an expert immediately'''

== In case of problem with remotely controlling the target ==
If the target control freezes, there are several ways to restore them, [https://logbooks.jlab.org/entry/4116279, described here].

== Expert personnel ==
The individuals responsible for checking that the cryogenic target is ready to take data  and setting its operating parameters  are shown in following table. Hall D contacts should be called first
Problems with normal operation of the cryogenic target should be referred to those individuals and any changes to their settings must be
approved by them. Additional experts may be trained by the system owner and their name and date added to this table.


{| border=1 
|+ Table:  Expert personnel for the Cryogenic Target
|- bgcolor=#DFDFDF  
! width=200px | Name    !!  width=100px | Extension !! Date of qualification 
|-
| Alexandre Deur   ||  align=center | Office: 757-269-7526 / Cell: 757-871-5931   ||  align=center | June 12, 2014
|-
| Chris Keith (Target group leader)       ||  align=center | Office: 757-269-5878 / Cell  757-746-9277 ||  align=center | June 12, 2014
 |-
| James Brock (Target group)       ||  align=center | Office: 757-269-7860 / Cell  757-871-5374 ||  align=center | June 12, 2014
|-
| Chris Carlin  (For computer control issues)        ||  align=center | Office: 757-269-5971 / Cell  757-559-1269 ||  align=center | June 12, 2014
  |}