• Topic ID: id_11038909
  • Version: 3.0
  • Date: Apr 9, 2020 8:42:58 PM

JEDI Noise Test (LS16, Ultra, Plus)

Prerequisites

The objective of this procedure is to verify that the DAS is not affected by noise created by the JEDI X-Ray Generator subsystem, in particular the High Voltage cables connecting the inverter to the tanks. Procedure summary:

  • Block collimator output so x-rays do not hit detector

  • Take scan

  • Analyze data and compare to specs

Procedure

  1. Set-up test scan:
    1. Remove gantry right side cover.
    2. Turn off the axial drive enable switch on the Service Switch Panel.
    3. Remove the mylar scan window.
    4. Rotate the gantry so that the tube is at the 6 o'clock position (tube at the bottom with the window facing up).
    5. Engage rotational lock. Check that the gantry is securely locked by attempting to rotate the gantry by hand.
    6. Fold a lead apron so that it is an inch or more thick. Cover the window of the tube with this lead apron so that x-rays cannot escape the tube.
    7. Open the Common Service Desktop Diagnostics button. Under the Image Chain menu select Diagnostic Data Collection (DDC).
    8. Select Stationary Scan - X-Rays On. Prescribe a scan with the following parameter values:

      • kV - 120

      • mA - 440

      • Gain - 10

      • Filter - BLOCKED

      • Slice Thickness - 16 X 1.25 MM

      • Cal Vectors - NONE

      note:

      Before pressing the scan enable button, verify gain has not changed by itself to some other value.

  2. Perform the scan.
  3. Analyze the data:
    1. Open the Common Service Desktop and press the Image Quality button.
    2. Select Scan Analysis.
    3. Find the scan that you just performed and select Plot MSD. After a few minutes, the plots for means and standard deviations should appear.
  4. Scroll through each of the standard deviation plots. Record the maximum values found in each range of channels in the middle two rows of Table 3.
  5. The test fails if any of the observed maximum values are greater than the spec. A likely cause is the positioning and securing of the high voltage cables between the tanks and inverter. This test must pass for the system to be used.

Finalization

No finalization steps.