E949 Range Stack Monitoring Systems
General Description
The main purpose of the Range Stack (RS) monitor system is:
- Calibration of the RS system
- Provides a new tool for understanding performance of the RS and of the energy resolution of E949.
- Allows for calibration of the RS on time scales less than 2 days (down to ~15 minutes).
- Will allow study of calibration variations within the ~4 sec spill.
- Rapid detection of problems in the RS
- Rapid detection of problems in the TD system
- Rapid detection of problems in the BV and BVL photon veto systems.
E949 RS Gain Monitoring system is based on a fiber optic network with a blue LED as
light source for a bundle of fibers. The system outline is presented in the picture below.
Main elements are:
- LED and Control photomultipliers housing boxes,
- fiber bundles,
- LED holders,
- LED drivers and power supplies,
- Control PMT holders with control PMTs,
- RS (or BV,BVL) PMT region fiber mounting structures.
For temperature stability reasons light sources, e.g. LED holders with
driving circuitry, are housed inside one temperature controlled box,
and
control PMTs for monitoring of LEDs light output on flash by flash
basis
are housed inside second temperature controlled box.
Each bundle of 175 fibers divided into 7 minibundles of 25 fibers has
its
own light source (NSPB320BS) with individual driver, and
covers six sectors of Range Stack or 12 sectors of
Barrel Veto and Barrel Veto Liner photomultipliers. One of this 25
fibers
minibundles is control for each big bundle and serves to monitor LED
light source stability. In total 14 bundles have been produced
(6 will
be used on each side of the detector + 2 spare ones).
- System Tests
- LED sources
- Fiber bundles
- Fiber - communication grade Mitsubishi Rayon Co. Ltd. Eska Premier GK-20
plastic fiber with following specs:
- Core diameter - 500 microns (0,5 mm),
- Refractive Index: Core - 1.492, Clad - 1.402
- Numerical Aperture - NA = 0.51,
- Temperature range - -55C to +85C,
- Attenuation - 0.18 dB/meter (0.14 dB/meter typical).
- fiber bundle:
Each bundle consists of 7 minibundles and common bundle tip. Each
minibundle has 25 fibers. Total length for each fiber is 11 meters for
working ones and 3 meters for control minibundle. Control minibundle
has its own tip. Working minibundles have 8.5 (for BV type bundles) to
10 (for RS type bundles) meters of fibers together in common PVC tube, and
1 to 2.5 meters of fibers separated individually in individual PVC
tubing.
- Bundle common tip
- Individual RS tip
- Control reference
- Bundle testing:
All 14 bundles were tested on setup which is shown here.
Light output of each individual fiber was determined relatively for each
bundle. After all 25 fibers of one minibundle were loaded into slits in
moving stage, the light output of each one was scanned when moving against
a photomultiplier window covered by screen with a vertical slit in it.
Each bundle was tested with its own LED/LED Holder and the same LED driver
card, but different LED driving pulse amplitude to make the light amount
about equal in output.
Test results:
- Fiberoptic bundles for E949 RS Monitor. - Technical Note.
BV/BVL Description (We also want to monitor these.)
-
Design Work
