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Some Remarks on Calibration of
BCAL.
 After recent
 I made some tests and
communications with
I didn’t measure any
the BCAL team, seems
deterioration of the
that we have to use a 2
signal.
wire cable, 5-10 cm,
from the board so as
 Do we need an
only the LED is
extension with the
attached on the light
trapezoidal L-Gs?
guide.
Pending issues.
Position and support of the board.
Piggy-back on the Amplifier board.
Any other suggestion from the engineers.
Protocol:
Any 2-wire protocol.
Serial Xon/Xoff as requested.
Intensity and Dynamic Range.
 Intensity can be Controlled by:
 Dc Voltage Adjustment.
 A piece of Film Filter between LED and the Light
Guide.
 Range:
 Using an LED with Longer Wavelength, Below the
Absorbing Band of the Fiber (not enough).
 Lower the Voltage of Near Side to a Safe Value, while
Pulsing the Far Side.
 Possible magic.
Test with trapezoidal light guide.
• There is enough space between the L-Gs for the LED
board.
• We positioned the board 3 cm from the photocathode.
• We used the demo, (baby) calorimeter.
• We measured the pulse high at the near and the far side.
• The ratio near / far was 8 to 10.
• Variation because of positioning.
Pictures of Light guide with LED
board.
Pictures of pulsesI
Near side
Far side
Pictures of pulses II
Near side
Far side
Other Approaches.
Return to fibers.
Not as elegant as it sounds.
• Splitters Cost ~ 2000 $ for 16 channels
• Inflexible
• Need Groove on Light Guide.