Log entry time 13:42:13 on June12,2004

Entry number 125450

This entry is a followup to: 125371

 
Proposed target load test
                             David Armstrong  June 12 '04

 I'd like to determine how much current the present He target
can really tolerate - this is important for next year's run
(assuming we can find a way around the septum heating limitations).

  Proposed plan:

1)  turn currents off of the septa (so they don't quench)

2) with target under present operating parameters:
   (input temp = 6.6 K, pressure = 175 psi, density = 0.129 gm/cc
    24 Hz fan speed) 
  ramp up beam current in steps of 5 muA starting with 5 muA
 waiting 3 minutes at each step. At each current, record
   - high power heater power
   - cell temp   (these should not change)
   - cell pressure   (these should not change)
   - 4 K coolant flow from CHL (observe carefully to ensure
     under 24 gm/s)
   - septa coil temperatures (right and left, upper and lower coils)
   - approx range of events numbers in HAPPEX DAQ (to allow us
     to look offline at lumi detector widths)

   Continue until either reach 50 muA or the high power heater power 
   is less than 50 W, whichever comes first. 

   - if 4 K coolant flow rises above 24 K, remove beam, and (if need
     be) adjust JT valve.

  Time required: about 40 minutes

3)  Adjust target operating point. We will raise target temperature to 
   about 7.2 K, keep pressure at 175 psi, and repeat the above scan.
   This should only reduce the density by about 4%, but (I hope) 
   should improve the cooling power considerably. That's what I'd
   like to verify.

  Time required: about 40 minutes

 Then I can produce plots as/in log entry 125371.
 

  Comments?