System test of the ATLAS muon spectrometer in the H8 test area: program for
year 2002
List of authors goes here
(to be completed by the different institutes involved in this document, please
add also name of people who contributed to THIS document):
………………..
Christoph Amelung CERN-EP Division
Jim Bensinger Brandeis University
Claude Guyot Saclay
Fabio Cerutti CERN-EP Division
Sandro Palestini CERN-EP Division
Ludovico Pontecorvo –INFN Roma
Joe Rothberg University of Washinton
Isabel Trigger CERN-EP Division
………………….
Abstract
The plans for the extension of the system test of the ATLAS muon spectrometer
in year 2002 are discussed. A brief description of the year 2002 scientific
program is given. The new components that must be added to the current set-up
to accomplish this program and the sharing of responsibility are discussed.
1. Introduction
High-momentum final-state muons are among the most promising and robust
signatures of physics to the LHC. To exploit this potential, the ATLAS
collaboration has designed a high-resolution muon spectrometer with stand-alone
triggering and momentum measurement capability over a wide range of transverse
momentum, pseudorapidity and azimuthal angle [1].
To achieve this goal, we have placed very demanding requirements on the Muon
system as a whole.
The precision chambers not only have to be built to very high standards of
performance, both mechanical and electronic, but their positions in the
spectrometer must be known at the level of the resolution of the chambers
themselves. This requires a sophisticated and extremely precise alignment
system.
The large size of the ATLAS muon system also presents a host of technological
problems; precision of tens of microns, on a scale of tens of meters, a
sophisticated trigger, a complicated magnetic field,
a large piece count, intricate structural supports, carefully choreographed
installation, and intricate routing of services to name just a few. We have
always expected that a full-scale test of one sector of the muon system would
be necessary [1]. It is self-evident that we cannot go from a single or few
chambers test to full-scale implementation of the muon system without a
meaningful system test on a reasonable scale.
There have been extensive tests of the various components of the muon system
already and they have been found to perform adequately. We do not anticipate
finding any fundamental error of design or implementation. However, many
detailed problems only show up in an integrated system on an adequate scale. To
confront these potential problems, we are planning a multi-step program to
validate the muon system before installation.
A first document with the general H8 test program was produced in 1999 [2]. The
first phase of this system test started in 2001 for both the barrel and
end-cap stands.
The second section of this document gives a brief overview of the current
set-up and of the results already achieved. Section three outlines the
scientific program for the 2002 run. Section four discusses the components
needed to reach these physics goals, together with the sharing of
responsibilities between the different institutes involved in the 2002 test
beam activities.
2. The current setup and the achievements in 2001
The final set-up foreseen for the H8 muon system test is already outlined in
[2]. During 2001 part of the set-up has been put in place.
2.1 The barrel stand
The current barrel stand consists of two regions, one dedicated to
autocalibration studies and the other dedicated to emulate a sector of the
ATLAS Barrel; in Fig 1 the barrel sector stand with a BIL and a BML chamber and
the autocalibration stand with a BIL chamber are shown.
In the first region a rotating support designed to house MDT chambers of BIS,
BIL and BOS type was placed on the beam line, and a BIL chamber and a BOS
chamber were tested and autocalibrated. In the second region two rails were
placed in a way to emulate the position of Inner and Middle chambers of the
sector at h=0.06
of the spectrometer. The same BIL chamber that was autocalibrated on the
rotating support and a BML chamber were placed on the rails and data were taken
with the two chamber in this configuration. Each chamber was read-out by four
mezzanine boards.
The data were then sent to an adapter-CSM0 readout chain and to the data
acquisition system via S-Link. On the beam line were present two trigger
systems, a large area one used to trigger on the beam halo, consisting of two
layers of scintillating slabs, covering an area of 60x100 cm2
, and a small area trigger (10x10 cm2
) centered on the beam line. A beam tracker chamber allowing to measure with
high precision two orthogonal coordinates on an area of 48x48 cm2
was operated to check the results obtained on the MDT autocalibration and
resolution.
A completely new DAQ system, based on the ATLAS DAQ-1 architecture, was
designed and implemented. It consisted of two VME readout crates (one for the
MDT CSM0s and the other for the TDC of the trackers), mastered by two RIO2
processors that were sending events fragments via S-Link to a ROS PC. Other PCs
were used for the run control, the monitoring, the data storage and the DCS.
The DCS system based on PVSS, allowed to record the temperature of the chambers
(8 values for each chamber), the temperature of the gas, the gas flow setting
and the gas pressure. The gas system was controlling both the gas composition
and the gas pressure with a few per mill precision.
Figure 1: A) The Barrel Sector (BIL & BML chambers), B) the rotating
support with a BIL chamber
A)
B)
The goals achieved with this set-up are:
Some of the results obtained in this first test can be found in [3].
2.2 The End-cap stand
The current set-up for the end-cap stand consists in three support structures
that emulate 1/8 of one end of the ATLAS Muon Spectrometer. In Fig 2 a photo of
the three end-cap support structures taken in summer 2001 is shown.
On each structure two alignment bars (fully equipped, measured and calibrated)
shall be mounted. The two EO bars are already in place, and the remaining four
should be installed before the end of 2001. Two phantom chambers per structure
should also be mounted on the frames. The two EO phantom chambers are already
mounted, the other four are already at CERN and will be mounted before December
2001.
Each alignment bar [4] is an aluminum tube of 80 mm outer diameter and up to
9600 mm length, equipped with Pt100 temperature sensors to monitor thermal
expansion of the bar, in-bar optical devices (RASNIKs) to monitor its
straightness, and surveyed platforms for mounting optical alignment devices
(double ended BCAMs[5]). The phantom chambers are equipped with proximity
sensors and RASNIKs masks to detect motion with respect to the alignment bars.
The Pt100 sensors are read out with the PVSS SCADA system used at CERN as the
agreed common program for DCS. The optical devices are driven and read out
using a custom VME driver board controlled by a small server program written in
C and running under Windows NT on an embedded PC in the VME crate. The server
communicates via the DIM protocol [6](based on TCP/IP calls) with a computer
running the PVSS SCADA system. The optical readout system is controlled using
this PVSS computer, which allows for graphical display of results, data
archiving and run control, as well as flexible testing of individual sensors
and groups of sensors. The optical sensors consist of CCD chips used to take
images of either point light sources (BCAMs) or coded masks (RASNIKs). The
images are analyzed by the server program running in the VME crate and the
results, consisting of two-dimensional position coordinates and (in the case of
RASNIKs) the magnification and rotation of the mask image with respect to the
mask, are sent to the PVSS computer. These data are then stored both in the
PVSS native archive format, which can be used for plotting alignment bar and
chamber information online with the PVSS interface, and in the form of simple
ASCII text files that are used by the alignment reconstruction code [7]. The
alignment bars are calibrated and measured in Freiburg, where a CMM machine
precisely measures the positions of the alignme
nt platforms. The two EO bars have already been measured, while the remaining
ones should be calibrated before the end of December 2001. More details about
the bar characteristics, calibration and measurement procedure can be found in
[8]. From the preliminary analysis of this data it has been shown that the
position of the alignment platforms can be predicted at the 20
m
m RMS level by using an analytical model of gravitational deformations,
complemented by the in-bar RASNIKs and temperature measurements.
Figure 2: The three end-cap support structure EI, EM and EO as seen from the
beam. The two phantom chambers installed on EO frame are also visible.
The phantom chambers have been equipped with in-plane RASNIKs, temperature
sensors and proximity platforms. A muon simulator consisting of one BCAM and
two light sources per chamber will be installed before the end of 2001.
The goals to be achieved with this set-up are many:
Another important benefit of running the End Cap test stand in 2002 will be the
opportunity to test the alignment devices readout and control system under
more realistic conditions in preparation for expanding the hardware and
software to the scale needed for ATLAS.
This program corresponds to what is quoted in [2] as the PHASE I of the H8
end-cap test. Of this program only a part has already been achieved in 2001.
This test program should be completed before spring 2002.
2.3 The DAQ system
Something about DAQ (Roma-1) setup in 2001 should be added here.
2.4 The DCS and other common items system
Something about the DCS (NTU) in 2001 should be added here
3. Set-up and scientific program for 2002
The ATLAS 2002 test beam schedule foresees an early start in April as shown in
Fig 3.
Figure 3: Preliminary ATLAS test beam schedule for 2002 (this is not the final
schedule. The running period will be probably delayed and shortened. The final
schedule will be added as soon as we have it)
The muon group requests at least two low-energy beam periods that are foreseen
for the weeks starting the 12 of June and 17 of July. During these periods
particles with momenta down to 10 GeV/c will be delivered in H8. In addition to
the runs where the muon group is the main user, parasite runs are also
possible when other subdetectors are taking data on the H8 beam line with the
exception of the runs with electrons and pions for the Liquid-Ar calorimeter.
3.1 The barrel stand
During 2002, the barrel stand shall be completed with 6 new chambers, namely
two BILs two BMLs and two BOLs. A new rail to place the BOL chambers shall be
mounted on the beam line.
To accomplish the projective alignment in the test beam environment the
chambers that should be used are of the following types:
A magnet will be used to fake tracks coming from the interaction region. With a
20 GeV/c muon beams an angular spread of
±
0.07 rad could be achieved with available magnets.
The characteristics of the proposed magnet are reported in Table 1.
Table 1: Characteristics of the proposed magned for the 2002 H8 setup.
The illuminated area will be about 1.5 m , 1 m and 0.6 m for the BOL, BML and
BIL stations respectively. The total number of read out channels will be about
672; at least 2 CSM and 3 CSM cable adapter will be needed to instrument the
irradiated area. The use of the magnet will enable us to test the barrel
alignment concept with straight tracks. The angular spread of the tracks allows
the alignment in space of the barrel chambers. This will require accurate
tracking over the full barrel sector. The chamber positions obtained by
tracking will be compared with the results of the projective alignment system.
. In addition to that the magnetic field will also give the necessary tracks
angular spread needed for autocalibration.
All the chambers should be equipped with projective and axial-praxial alignment
platforms and sensors. The DCS system should be capable of reading out all the
alignment sensors. Specific for the H8 test, eight new alignment platforms
should be produced and installed on the chambers as showed in Fig4.
Figure 4: Alignment Platforms and sensors for the 6 chambers of the Barrel
Stand
Moreover a test of integration between the trigger chambers (RPC) and the BML
chambers could be performed. The common RPC-MDT support will be mounted and
tested. Possible interference, both mechanical and electrical between the RPC
and the MDT will be checked. The purposes of this upgrade of the experimental
set up are the following:
3.2 The End-cap stand
The end-cap test in 2002 should evolve from the alignment test phase (referred
to as PHASE-I) to a more complete system test including the alignment of real
MDT chambers. At least two chambers per structure should be mounted and
operated. The chambers that are needed (the ones illuminated by the H8 beam)
are EIS1, EIL1, EMS2, EML2, EOS3 and EOL3. The purposes of this upgrade of the
experimental set up are the following:
This program should be accomplished with the data taken in the 2002 beam
period. 3.3 DAQ
The Data Acquisition System should be upgraded to permit the reading out of the
RPC signals, a new crate with RPC read-out modules, read-out CPU and S-Link
data transmission will be needed. If the first level trigger electronics will
be available by the time of the test beam also a test of the trigger concept
and electronics could be performed.
(To be completed by MUON-DAQ group)
3.4 Barrel alignment test program
More detailed description of the barrel alignment setup and DAQ (to be
completed by C.Guyot and F.Linde).
3.5 DCS and other Common items
Some of the components of the test beam should be in common for the EC and the
barrel stand. This is an important part of our test where the control via the
DCS and DAQ systems of different components of the ATLAS muon spectrometer will
be tested.
(To be completed by DCS muon group)
4. Sharing of responsibilities for the 2002 test activities
It is important to define the share of responsibilities and costs between the
different institutes participating at this second phase of the H8 test. In the
following subsections the missing components needed to achieve the goals
described in section 3 are detailed together with the list of the institutes
that are responsible for these items.
4.1 The barrel stand
The components, needed for the completion of Barrel test, are:
If the RPC will participate to the 2002 test beam these items will be needed:
The full list of components needed for the barrel stand completion in 2002 is
detailed in Table 2. A more detailed list, including the cost estimate and the
sharing of responsibilities for each component is reported in Table 4.
Table 2: List of components needed for the 2002-barrel test program as
explained in the text.
4.2 The End-cap stand
The components needed to complete the EC test:
The full list of components needed for the end-cap stand completion is detailed
in Table 3. A more detailed list, including the cost estimate and the sharing
of responsibilities for each component is reported in Table 4.
Table 3: List of components needed for the 2002 end-cap test program as
explained in the text.
[1] The ATLAS muon TDR
[2] J.Bensinger et al
., Muon Spectrometer Test Programme in H8, This document can be found at:
http://cerutti.home.cern.ch/cerutti/h8datcha_propo_feb00.pdf
[3] G.Avolio et al., First results of the 2001 MDT chambers beam test
, ATLAS-MUON –2000-022
[4] A. Schricker,
Alignment Bars for the Muon Endcap Alignment, ATLAS note in preparation;
http://axl.home.cern.ch/Axl/bars.htm.
[5] K. Hashemi and J. Bensinger,
The BCAM Camera, ATLAS note
ATL-MUON-2000-024; K. Hashemi and J. Bensinger, The ATLAS BCAM, ATLAS
note in preparation. [6]
DIM, a Portable, Light Weight Package for Information Publishing, Data
Transfer and Inter-process Communication,
C. Gaspar, M. Dönszelmann, Ph. Charpentier. Presented at the
International Conference on Computing in High Energy and Nuclear Physics
(Padova, Italy, 1-11 February 2000).
[7] Ch. Amelung, Muon Spectrometer Alignment in ATLAS: A Generalized Approach
to Simulation, ATLAS note ATL-COM-MUON-2001-013; The ARAMYS Software, ATLAS
note in preparation.
[8] Ch. Amelung and A. Schricker, Calibration of Alignment Bars for the ATLAS
Muon Spectrometer Endcap, ATLAS note in preparation.
Type
Length (mm)
BxL (Tm)
Useful Aperture (mm) MBPL
2000
4.06-3.11
300 x 110-200 
Bibliography
