Detector Construction Page
Leader: Michael Strang
This is the FPD Detector construction page. It will describe
the current status of the construction of the scintillating
fiber detector.
To build the detectors, a scintillating fiber is spliced
onto clear waveguide fiber and glued into place with Bicron
epoxy on plastic frames with four fibers per channel. The
detectors consist of 6 planes (U, U', X, X', V, V') and a
trigger scintillator. The primed frames are offset from the
unprimed frames by 1/3 of a fiber and the U/V frames (20
channels) are rotated +/-45 degrees with respect to the X
frames (16 channels). The detectors are read out using 16
channel Multi Anode Photo Multiplier tubes with a reused Run
I L0 PMT for the trigger. A modified Muon Light Mixing Box is
used to calibrate the MAPMTs and L0 PMTs during the run. For
more information on the detectors, please see the FPD
Detector page.
The task of building the detectors consists of many
different things. First, the delivery of the fibers and the
frames. Second, the splicing of the fibers and the gluing of
the detectors. Third, final polishing of the detectors at
FNAL. Fourth, mapping of the fiber locations in the detector.
Fifth, testing of the PMTs to be put in the cartridges.
Sixth, construction of the cartridges and insertion of the
detectors. The current status of these tasks can be found
below. The current goal is to have 10 full detectors ready
for the September shutdown.
At the bottom of the
page, there are links to various talks I have given on the
detector production and its status.
Fibers / Frames
The fibers and frames are the heart of the detector.
Fibers: Scintillating fibers from
Bicron are spliced to clear waveguide fibers and then
insterted into a plastic frame. The fibers are cut to
length, polished and qualified at FNAL then shipped to UTA
for use.
Frames: The frames are cast at
FNAL, qualified, sanded and drilled then sent to UTA for
use.
Status
-
June 19, 2001:
-
Frames: Currently, there
are sufficient frames at UTA to construct the 10
detectors wanted by September. The remaining
frames are at FNAL undergoing final preparation.
-
Fibers: Over half of the
required fibers are at UTA to be spliced while
the rest are currently at FNAL being cut,
polished and qualified.
-
September 30, 2001:
-
Frames: All frames, cookies and
sockets have been produced. A few are undergoing final sanding
and modifications and the rest have been sent to UTA.
-
Fibers: All fibers have been cut and
polished, qualified and delivered to UTA. There they are being sorted by
size before use.
Splicing / Gluing
Splicing: The two types of fibers,
once at UTA, are spliced together using a the MSU style
splicing machine. This machine uses glass tubes to hold the
fibers, pressure to keep the fibers in contact and heat
from a gold-coated halogen projector bulb to melt the
fibers together.
The size and placement of the glass tubes is critical in
the quality of the splice. Since we are forced to perform
"naked" splices (i.e. no heat shrink tubing for strenght),
the glass pieces wear out much more quickly that we would
otherwise hope. The replacement of these tubes is very much
of an art and the machine can sometimes be down for as long
as a week when trying to get the machine to work again.
The fiber size is also critical since the friction of the
glass tubes against the fibers can make or break a splice.
For this reason, the cut fibers have to be sorted by size
before they can be spliced. We nominally ordered 0.80
fibers (the frames can accomidate 0.83) but the majority of
fibers are 0.78 and below. Unfortunately, we are having a
difficult time getting glass pieces that work with the 0.78
fibers reliably.
We also have a problem with swelling of the fibers. A 0.77
fiber will swell after splicing to ~0.82 near the splice
point. Fortunately, the frames can accomodate this swell,
but it grows over time and when it is consistently 0.83 we
need to replace glass tubes.
Gluing: Once the fibers are
spliced, they are glued into the frames. The procedure
involves the alignment of the splice points for 4 fibers
that are then aligned to the edge of the active area in the
frame. The procedre can be seen here. (
doc)
Status
-
June 19, 2001:
-
Splicing: We have
spliced enough fibers for 8 1/2 detectors.
Currently the splicing machine has friction
problems so the glass pieces are being reset.
-
Gluing: 8 detectors have
been completely glued and delivered to FNAL.
Another is partially glued awaiting the return of
Petra to UTA. 2 of these are prototype detectors
and of inferior quality do to swelling of the
splice point.
-
September 30, 2001:
-
Splicing: The splicing is going very
slow due to the difficulty in using the glass pieces. Additional
pieces have been ordered with some slightly larger than before to
accomodate the larger fibers. After the shutdown we will investigate
the Mississippi design of the splicing machine for possible use with
the remaining detectors.
-
Splicing: Detectors 1, 2, 3, 4, 5, 6, Pr1, Pr2 are
at FNAL. Detectors 7 and 8 are currently being glued.
Polishing
Before the U, V and X frames can be fully assembled into
the final detector, it needs to undergo some final
polishing and aluminizing. The first step is to take the U
and V frames to Pat Richards in Lab 6 so the inside edge
can be cut and polished. They are then delivered to Eileen
Hahn at Lab 7 to be aluminized. Once aluminized, the
detecter can be assembled into a block. After this, Pat
Richards can cut and polish the bottom of the detector. The
the detector is mapped. After mapping, Eileen can coat the
bottom and the detector is ready to be assembled into a
cartridge.
Status
-
June 19, 2001: 4 detectors are fully assembled, 2
have been polished on the inner surface and 2 are in
prep to be polished.
-
September 30, 2001: Detectors 1 and 2, Pr1 and Pr2 are all polished
and assembled. Detectors 3, 4, 5, 6 are assembled and at Lab 6 to be
polished.
Mapping
As a new step in the preparation of the detectors, the
actual location of the fibers in the frames is going to be
mapped out using a precision optical scanner with a
resolution of 2 microns located in the clean room at Lab 3.
This will allow us to reconstruct the detectors in their
real configuration rather than an idealized 0.80 fiber
configuration.
Four detectors are too far along in the process (i.e.
assembled into cartridges) to easily undergo this mapping.
The other four will be mapped as soon as they can and the
others will be mapped in September.
Status
-
June 19, 2001: The optical scanning device needs to
have a support plate built for it to support the
cookies. After this, it should be relatively easy to
map the detectors.
-
September 30, 2001: The support plate is built and as soon as
the detectors are polished they will be mapped.
PMT Testing
We have recently ordered 64 new MAPMTs from Hamamatsu in
order to be able to instrument 10 detectors by September.
We want to have some understanding of these PMTs so we will
use an LMB setup in the ICD test stand in DAB to gather
information about the channel by channel behavior of the
tubes.
We will then bundle the tubes into groups of 7 tubes that
behave similarly. We will also perform these tests on the
L0 PMTs so they can be bundled into groups of 4 similarly
behaving tubes.
Status
-
June 19, 2001: Looking into adapting the ICD
teststand to our purposes. A LMB interface needs to
be constructed and ready for when the tubes arrive in
August.
-
September 30, 2001: 63 MAPMTs have been delivered from Hamamatsu.
They are currently undergoing testing on the 3rd floor DAB. We are
using the LMB to send light to the each of the 16 channels and then
using LeCroy 2249 ADCs to look at the ADC output from each channel for
-800V and -940V. We will get an average ADC count over the 16 channels
and the max and min ADC counts and use this information to group the
tubes.
We will also look at some tubes in 10V steps from 800 to 940 to determine
how the gain grows with voltage as well as sending light to only one channel
and looking at the possibility of cross talk.
We will also use the LMB to look at L0 tubes but the majority of tubes
are currently in the tunnel and will be measured during the shutdown.
Cartridge Assembly
The assembly of the cartridge consists of assembling many
machined parts with the ultimate goal of holding the
detector and PMTs in place when inserted into the Roman Pot
in the tunnel.
Here you can find
detailed instructions on how to assemble the cartridges as
well as including the detectors and PMTs. (Click your back
button to come back here after looking at it.)
Also, a new hole needs to be drilled in all of the tubes
for an LMB fiber to probe the L0 PMT.
Status
-
June 19, 2001: Currently we have two full detectors
assembled, 12 cartridges with only L0 PMTs and 2
cartridge bottoms with prototype detectors installed.
The empty cartridges will have PMTs and detectors
added when available and the remaining cartridges
will be assembled awaiting all the detectors and
PMTs. We will have a total of 18 cartridges assembled
when completed.
-
September 30, 2001: We have assembled/modified the remaining cartridge
bottoms and are awaiting the PMT tests to assemble the cartridge tops.
We have decided to modify the tops to allow the use of mu-metal shielding
of the L0 tubes.
Locations of cartridge parts:
We have 2 cartridge bottoms with Pr1 and Pr2 at Lab 3. They need to be modified.
We have 12 cartridge bottoms in the tunnel. 2 contain detectors 1 and 2. They need to
be modified
We have 10 cartridge tops in the tunnel, 2 of which contain MAPMTs. They all
need to be modified.
We have 4 cartridge bottoms that have been modified and assembled at Lab 3.
We have 6 cartridge tops modified awaiting MAPMTs at Lab 3.
We have 2 cartridge tops at Lab 6 with bad L0 tubes that need to be modified.
As things are assembled, we will give a number to each cartridge bottom and top. We
will list what detectors and SN tubes are in each and the location of each in the tunnel.
Talks
Here are links to various talks I have given about the
detector production.
-
Here is a link to a talk I gave at UTA for the DOE
representative on July 22, 2000 (ppt)
-
Here is a link to a talk I gave at a collaboration
meeting on March 13, 2001 (ppt)
-
Here is a link to a talk I gave at the Graduate Research
Symposium at UTA on April 5, 2001 (ppt)
-
Here is a link to a talk I gave at the April meeting of the APS
this year in Washington D.C. (ppt)
You can also get to talks that contain detector
construction information on my root
FPD page.
If you have any questions or comments, please mail me
at: strang@fnal.gov
This page last updated: 30-Sep-2001 03:04 AM (UTC -05:00)