meeting with St. Gobain

[Elton Smith <elton@jlab.org>]

This afternoon we met with representatives from St.Gobain that were
visiting JLab. We meet in Elke's office. Present were Elke, Elton, and
Beni. (Carl missed the meeting due to a doctor's appointment with his
son).

Notes on the meeting with Mike Kusner and Timoth Parker
St. Gobain (formerly Bicron)
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Fiber Testing: Attenuation measurements performed from each preform that
generates approximaterly 1km of fiber. Atten measurement performed on 2-3m
long samples.

Production: During production they run around the clock with about 5
towers, providing about 3 km/tower/day. During productions for CHORUS,
they produced 50 km/week. In their proposal, they estimate they will be
producing 120 km/month after ramp up.

Documentation: St. Gobain promised to send us their measurements of all
the fibers that they have shipped us. This includes the early 4.1 m long
fibers to Regina, the shipment of fibers in Jan, and some resent samples
sent to us last week.

Budgetary estimates: For budgetary estimates, they estimate BCF-12 is
about 15% less expensive than BCF-20. All production of plastics (Crystal
Division Office) is in Newbury, OH. [i.e. exchange rates with France
should not directly influence the price].

Absolute Light Output: The nominal photon production is 8,000. This holds
for styrene plastics with tertiary light production, which applies to
BCF-20 and BCF-12. Mike believes the absolute number of photons produced
for both blue and green should be close. Of course much of the blue light
is indeed absorbed close to the source which reduces the effective light
yield. [Other fibers such as BCF-428 with additional transitions, are down
in light output]. The most efficient transitions are for 3HF with a single
transition between UV and green.  However, the drawbacks are slower rise
times and photosensitive materials.

Question: I passed on the inquiry from George/Zisis from this morning's
working group meeting. The St.Gobain procedures seemed imply that blue
light needs a longer distance to absorb than the green. Mike indicated
that the minimum thickness of their samples (5 mm) was simply chosen for
convenience in that they perform the light yield test (with a source) in
addition to the spetrum measurement with the spectrometer. The absorption
of the 390 nm exciting spectra has a mean free path of 150 microns and is
the same for both blue and green. For the spectra only measurements, their
samples could actually be thinner.

N.B. Elke asked about the inquiry from Werner to their office regarding
scintillators for the start counter. They are in the process of responding
to him.


Cheers, Elton.

Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite # 16
Newport News, VA 23606
elton@jlab.org
(757) 269-7625
(757) 269-6331 fax