Accelerator Handbook

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
====== Accelerator Start-up ======

1.	**Verify Initial Machine Voltage setup:**

Initial conditions on TPS:
  * TPS POWER:				ON
  * SLIT, GVM, CPO, PROBE:		All on
  * OVERVOLTAGE PROTECTION:	        Disable
  * CONTROL MODE:			GVM
  * CONTROL GAIN:			Zero
  * CPO GAIN:				7-9
  * TERMINAL VOLTAGE dial:		Zero
  * BIAS CURRENT:			40

Initial conditions on Charging Controller:
  * Key:				ON
  * Power:				ON
  * INTERLOCKS OK:			Green
  * CHAIN MOTORS 1, 2, 3:		Lights dark
  * CHARGING VOLTAGE dial:		0.10
  * POWER SUPPLIES:			OFF

Initial condition on SHUTDOWN MODULE:
  * POWER:   Red Light On
  * CABLE:   Green Light On




a.  Switch the POWER SUPPLIES to ON, the yellow light should come on. Switch CHAIN MOTORS to ON, lights 1, 2, and 3 should all come on.  Begin to increase the CHARGING VOLTAGE  while observing the TERMINAL VOLTAGE and the GRID VOLTAGE.  DO NOT allow the GRID VOLTAGE to become more negative than   **-5** VDC.  **NOTE: If you will be raising the terminal voltage to 3.5MV or higher double click the TANDEMWATCH icon on the alphatross terminal monitor.  After approximately 1 minute, the tandemwatch graph should appear on that monitor.  Aleo, check LE tube conditioning by; 1. In the light yellow terminal window, type the command "plot magnet".  This will open a graph that will plot in high sensitivity the LE tube vacuum to watch for tube conditioning.  2. Now, also in the light yellow terminal window, type the command "plotlevacuum".  The plot window should begin plotting a high resolution view of the LE vacuum.  If spikes in vacuum are observed when raising the terminal voltage, stop increasing the terminal voltage and wait until the vacuum returns to the baseline value.  Continue increasing slowly to the desired terminal voltage while continuously monitoring the LE tube vacuum and pausing when increases are seen.  After the desired terminal voltage is reached, the program watching the vacuum can be stopped by entering c/r in the terminal window and the plot can be closed.
**
b.	Continue to increase the CHARGING VOLTAGE until you reach the approximate TERMINAL VOLTAGE **__OR__** until you begin seeing any corona current.  If you begin seeing corona current, move the corona points out until no corona current is seen.



**2.	Corona Probe Adjustment**

After reaching the approximate desired terminal voltage with no corona current present, begin moving the corona points in.  Maintain the desired approximate terminal voltage by increasing the UPCHARGE and iteratively move the corona points in while restoring the terminal voltage with the UPCHARGE.  The CORONA PROBE CURRENT will rise until it reaches the value set by the BIAS CURRENT.  After that, the GRID VOLTAGE will change to keep the CORONA PROBE CURRENT at the set value.  The goal is to balance the UPCHARGE and CORONA PROBE POSITION so that you have the desired TERMINAL VOLTAGE and **-5** VDC on the GRID VOLTAGE (The GRID VOLTAGE may never reach -5 VDC when running at ultra low Terminal energy, E < 0.300 MV, do the best you can).  Do (a) or (b) as needed:

a.	Move the CORONA PROBE POSITION “IN” to make the GRID VOLTAGE more negative.  This may require you to adjust the UPCHARGE to maintain TERMINAL VOLTAGE.

b.	Move the CORONA PROBE POSITION “OUT” to make the GRID VOLTAGE less negative.  This may require you to adjust the UPCHARGE to maintain TERMINAL VOLTAGE.

c.      If the low energy cup current is > 5 uA, put the beam into the high energy farady cup and tune for maximum current before proceeding to step 3.



**3.	Establish Control**

a.	Set the TERMINAL VOLTAGE Dial to the desired value.  The dial is 2 turns per MV (set the dial to twice the GVM you want).  You may have to add some upcharge after setting the dial.  

b.	Slowly raise the CONTROL GAIN to 2-3 for low current beams, around 5 for high current beams.  The system is now controlling in GVM mode.

c.	Make fine adjustments to the TERMINAL VOLTAGE Dial to reach exactly the desired GVM value.

d.	Switch OVERVOLTAGE PROTECTION to ENABLE.

**4.	Beam Transport**

a.      Use the magnet predictor tool and set Quad 1 to the predicted value.

b.	Tune beam and send it around the properly configured Analyzing Magnet. 

c.	You may need to make adjustments to the TERMINAL VOLTAGE dial to get the terminal to the proper energy for transmission around the magnet and fairly balanced current on the slits. 

d.	When current is present on the LE and HE Slit current meters you may then switch the Control Mode to AUTO (middle position) and the SLIT control light should illuminate.  If there is instability in slit control you may try raising the CONTROL GAIN more.  If the slit currents are not balanced when in slit control, make slight adjustments in the CHARGING VOLTAGE to balance the slit currents.

e.	When in AUTO control the machine will go back to GVM control anytime the beam is interrupted.
Accelerator Handbook

User Tools

Site Tools

Page Tools
