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User name Jixie
Log entry time 23:07:44 on April 9,2012
Entry number 372284
keyword=How to make vertical correction to target insertSince the target insert is 10.81 mm upstream from the target center, when the target field is on the beam trajectory at the insert plane will below the horizontal plane. The vertical coordinate (y) of the beam at the insert is called "vertical offset (Y_off)" here.
This offset is negligible for gep or when beam go to local dump, but not for g2p when beam go to the HallA dump. Here are the vertical offsets for various beam energies in g2p settings:
beam(GeV) Y_off(mm) target_field encoder_offset
2.254 -0.5 2.5T -14764
1.706 -0.7 2.5T -20669
1.157 -1.0 2.5T -29528
How to make this correction?
1) Put this encoder_offset into 'target insert gui' when we move the target insert to C12_Hole; (In the target control gui (Fig. 1), click on 'Move Target', the 'target insert gui' window (Fig. 2) will pop up.)
2) Ask MCC to unlock BPM 1H01 and 1H05B. Try to center the beam with the carbon hole, change beam position if necessary. Once determine the center, lock the beam again.
3) Reset the offset in 'target insert gui' to zero.
4) Change the target position as usual.
FIGURE 1
FIGURE 2
