Status of OPERA RPC production.

1
Status of OPERA RPC production.

• A. Garfagnini
• Opera collaboration meeting Nagoya, 12 march
  2002

• RPC production at GT
• Schedule for OPERA in 2002
• Summary of the quality control tests
• results from the OPERA prototypes
• Status of LNGS infrastructures for RPC mass
  production tests.

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General Tecnica (GT) s.r.l.

• Company located at Colli (Frosinone), 120 km
  south-east of Rome.
• Producer of tooling for assembly lines for cars
  radiators (working mainly for the FIAT factory
  near Cassino).
• Unique producer of bakelite RPCs in Italy.
• Past productions L3 ( 600 m2) and BABAR
• Running productions BABAR, ARGO, ATLAS, CMS,
  ALICE, OPERA,

RPC production buldings 700 m2
Factory owner and technical director Mr.
Fabrizi. Responsible of production and quality
control Mr. Fiore. 10 technicians are currently
involved in the RPC assembly and strips
preparation and integration.
3
RPC production history (2001)
All the bakelite RPCs for the INFN experiments
are produced by General Tecnica. In order to
coordinate the experiments needs, a INFN
committee had been formed, with the task of
analyze and improve the processing procedure and
to interact between the INFN and the
factory. After a successful benckmark performed
last year, the company produced 12 RPCs/day, on
average, for one month. The BABAR experiment had
a key role in the development and improvements of
the production.
4
RPC production (2002)
This year the production has been boosted to 18
RPC/day in order to fulfill all the requirements
(mainly dominated by the LHC experiments) new
tools and procedures have been introduced the
gluing step has been automated, the glue curing
places - pizzeria have been doubled, and a
new building for the storage of the materials is
under construction. The committee, lead by
S.Morganti (INFN Rome-1st university and BABAR),
has regular meetings where production schedules
and results are discussed each experiment has at
least one representative person which is contact
with the committee and follows its RPCs
production at General Tecnica (next meeting,
march 14th in Rome).
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RPC production (1)
According to the above schedule OPERA production
will start in June 2002 574 RPCs will be
produced by the end of 2002, (always lt 30 of the
total share/month).
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RPC production (2)

• The offer for the OPERA production is at the
  moment in a stand-by position, as many of the
  spectrometer components.
• Nevertheless, the first set of bakelite (105
  layers, high resistivity from BABAR) has been
  received and inspected at GT
• 16 rejected due to same production defect
  (feedback w/ PanPla needed).
• New layers expected soon (build a buffer at GT
  and LNGS).
• ? Once the CERN and INFN positions will become
  clear, ready to start.

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Quality control tests

• The OPERA quality control checks are strongly
  based on those developed for the BABAR
  experiments (S.Morganti, et al.
  http//babar.roma1.infn.it/morganti/rpcwww/).
• They can be classified into
• mechanical tests
• gas tightness (leakage) and spacers gluing
  (first bubble push)
• electrical tests
• HV conditioning and IV curves.
• response to elementary particles
• chamber radiography and efficiency curves.
• All the quality control tests will be performed
  at the Gran Sasso laboratories (LNGS), where a
  dedicated hall (lab2) has been assigned.
• Results on the QC tests for the prototypes,
  performed at GT using the BABAR equipment, are
  summarized in the followings.

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OPERA prototypes

• 16 full-size prototypes have been produced by the
  end of 2001
• 1 has been used by GT to check the oil coating
  quality
• 1 rejected due to bakelite defects (used as dummy
  for test calibration)
• 2 rejected during mechanical tests
• 12 chambers pass the quality controls (12/15 ?
  0.8)
• 9 sent to CERN
• 3 to LNGS.

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Mechanical tests summary (1)

• mechanical tests
• no gas leakage found
• for one chamber spacers disconnect while
  inflating
• one chamber is spoiled during test, human error,
  (water fills the gap).
• The two rejected RPCs have been opened to check
  oil coating. First spacer, pops at 15 and 70
  mbar (water filled chamber).

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Push test
AIM Identify and localize unglued spacers (can
cause inefficiencies). The GAP with internal
pressure will experiment a small deformation in
the presence of an unglued spacer. The
deformation is neutralized with small cylinders
(9/row) which are moved across the chamber. The
pressure sensor will detect a small volume
deformation due to one ore more unglued spacers
and spacers glued away form the nominal position.
11
Push test results
One tested chamber had several unglued spacers
(no glue on one side was find after having opened
the chamber. The final test will be
completely automated, reducing the operator time
and improving the sensitivity of the test.
12
Electrical tests summary
The chambers are filled and fluxed w/ gas for
some time (time required to exchange several gas
volumes) before the first IV curve is
performed. An I/V curve is performed from 0 to 8
kV (up to 7kV for the prototypes). Dust residuals
are burned keeping the GAP for some time at
fixed voltage. Annealing effect is seen for IV
curves measured at different times.
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Cosmic rays tests

• A cosmic test station is being setup.
• Big involvement for the LNGS electronic and
  mechanical workshops, lead by C.Gustavino and
  L.Tatananni, respectively.
• Trigger
• 2 planes (4?4 m2 each) using glass RPCs
• 1 cm strips (flat cables glued on polypropylene)
• 1st coordinate, digital readout (MACRO GSC
  cards)
• 2nd coordinate using time information (?t lt 50
  ps).
• Bakelite RPCs
• 3 boxes (12 ? 3) under test at once
• use MACRO readout strips (3 cm) for both
  coordinates
• digital readout (MACRO GSC).

m
Boxes
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LNGS infrastructures

• Experimental hall free for OPERA
• Started the process for the offers for the gas
  system (4 independent distribution point inside
  the hall gas mixed inside)
• Trigger planes
• Mechanical structure in advanced status, started
  to mount the structures inside the hall
• RPCs glass delivered, start to assemble the
  detectors (16 m2)
• material for strips (flat cable polypropylene
  planes) available
• electronics for t1-t2 under testing, final
  production will start soon.
• RPC under test
• measures fixed, 2 box prototypes ordered
• material for strips available (from MACRO)
• card for signal inversion (HV 4kV) designed,
  prototypes will be soon available for testing.

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LNGS infrastructures (2)

• DAQ under development, will use a system similar
  to that currently used for MONOLITH prototype and
  for GSC-II project), will start to exercise with
  the OPERA RPC prototypes available at LNGS.
• For the mechanical tests work is underway
  automatic push test prepared by E.Buccheri (Roma1
  technician, temporarily assigned to the project).
• Readout and analysis programs under development.
• Idea to provide a database, with web interface,
  storing all the tests parameters, up to the RPC
  radiography.

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Summary
The QC steps have been defined and work has
started some months are needed before the system
is fully assembled, the software completed and
debugged and the system becomes fully operational
for the mass production control. We are thankful
to the BABAR collaboration, in particular to
S.Morganti, for their help we have learned from
their experience and selected a QC system which
is essential for the large production of the
OPERA RPCs (more than 1500 GAPs). The LNGS
technical support has been very cooperative and
is essential for a successful realization of the
whole QC machinery.