A year of ATLAS preparation.
Steve Snow
New Year 2006
What I did last year
• Inner detector magnetic field map fit.
• SCT detector alignment.
• NMR probe preparation.
• Write/edit endcap module paper
• SCT status paper at PSD7.
• Organise seminars
• SuperNEMO tracker.
•
CALICE thermal simulation.
My ATLAS aims
The resolution of tracks reconstructed in ATLAS ID should be:
• Good enough for some physics from the first collisions
• Rapidly improved by using track-based alignment tools
• Eventually good enough that track systematic errors do not
dominate the measurement mW to ~15 MeV
This and following slides
copied from Paul
Miyagawa's talk at the
2nd ATLAS magnetic field
workshop
•
•
•
Field map objectives
A useful test of the Standard Model would be measurement of W mass with
uncertainty of 25 MeV per lepton type per experiment.
W mass derived from the position of the falling edge of the transverse mass
distribution.
Momentum scale will be dominant uncertainty in W mass measurement:
– Need to keep uncertainty in momentum down to ~15 MeV.
•
Measure isolated muon tracks with pT ~ 40 GeV over large range of η:
– Uncertainty in energy loss negligible.
– Concentrate on alignment and B-field.
•
Momentum accuracy depends on ∫ r(rmax - r)Bzdr :
– Field at intermediate radii, as measured by the sagitta, is most important.
•
Typical sagitta will be ~1 mm and target accuracy would be 0.02%, implying a
systematic error on sagitta of 0.02 μm:
– Technically impossible!
– Will need to use Z mass, which is nearby and very well known.
•
•
In reality, the limit on silicon alignment, even with infinite statistics and ideal
algorithms, will be ~1 μm.
We target an accuracy of 0.05% on sagitta to ensure that B-field measurement
is not the limiting factor on momentum accuracy.
Field shape.
25000
20000
Z component
15000
5000
R component
0
0
0.
27
2
0.
54
4
0.
81
6
1.
08
8
1.
36
1.
63
2
1.
90
4
2.
17
6
2.
44
8
2.
72
2.
99
2
3.
26
4
Field (gauss)
10000
-5000
Bending power
-10000
-15000
-20000
Z (m)
r=0.2
r=0.4
r=0.6
r=0.8
r=1.0
r=1.2
r=0.2
r=0.4
r=0.6
r=0.8
r=1.0
r= 1.2
r=0.2
r=0.4
r=0.6
r=0.8
r=1.0
r=1.2
The field is very non-uniform at the ends of the coil; the Z component drops off
and the R component rises sharply at z=2.65 m. Also plotted is the bending
power per unit of radial travel for straight tracks coming from the origin.
Mapper Survey Requirements
2.
3
1.
9
1.
5
1.
1
0.
7
0.
3
-0
.1
-0
.9
-0
.5
-1
.3
-1
.7
-2
.1
phi 7
phi 8
phi 9
phi 10
-6
-8
Pseudorapidity
Effect of 0.1 mrad rotation around the X axis
-3
phi 10
-4
-4
Pseudorapidity
2.
3
phi 7
phi 8
phi 9
phi 10
-6
-8
-5
1.
9
-2
1.
5
phi 7
phi 8
phi 9
1.
1
2.
3
1.
9
1.
5
1.
1
0.
7
0.
3
-0
.1
-0
.9
-0
.5
-1
.3
-1
.7
-2
.1
-2
phi 5
phi 6
0
0.
7
phi 5
phi 6
0
phi 3
phi 4
2
0.
3
1
4
-0
.1
phi 3
phi 4
phi 1
phi 2
-0
.9
-0
.5
2
6
-1
.3
phi 1
phi 2
3
-2
.5
-4
Effect of 1 mm displacement in Z direction
4
Relative sagitta error x 10^4
-2
8
5
-1
phi 5
phi 6
0
-1
.7
•
phi 3
phi 4
2
-2
.1
•
phi 1
phi 2
4
-2
.5
•
Effect of 1 mm displacement in X direction
6
-2
.5
•
•
8
Relative sagitta error x 10^4
At first workshop, survey requirements
of mapper machine relative to Inner
Detector were reported as ~1 mm and
~0.2 mrad.
Reinvestigated these requirements.
1 mm survey error in x (or y) significant
for high η tracks.
1 mm survey error in z significant for
endcap tracks.
0.1 mrad rotation around x (or y) axis
significant for high η tracks.
Conclusions remain unchanged.
Relative sagitta error x 10^4
•
Pseudorapidity
Field Mapping Simulation
•
•
•
•
Field model sampled on a grid of 90 zpositions × 8 -angles (defined by encoder
values of machine).
4 calibration points (2 near centre, 2 near one
end) visited after every 25 measurements.
Used current design of machine to determine
positions of 48 Hall + 1 NMR probes.
At each map point, wrote the following data
to file:
– Time stamp
– Solenoid current
– z and  encoder values
– Field modulus measured by 5 NMR
probes (1 moving + 4 fixed)
– 3 field components measured by 48 Hall
probes
Simulated Errors
Six cumulative levels of error added to simulated data:
1.
No errors.
2.
Random errors in each measurement of:
•
•
•
3.
Drifts by random walk process in each measurement of:
•
•
4.
6.
Solenoid current, 1 A
Each component of Hall probe B-field, 0.1 G
Random calibration scale and alignment errors, which are constant for each
run:
•
•
5.
Solenoid current, 1 A
NMR B-field modulus, 0.1 G
Each component of Hall probe B-field, 3 G
Each component of Hall probe B-field, 0.05% scale
Rotation about 3 axes of each Hall probe triplet, 1 mrad
Symmetry axis of field model displaced and rotated relative to the mapper
machine axis. These misalignments are assumed to be measured perfectly
by the surveyors.
Each Hall probe triplet has a systematic rotation of 1 mrad about the axis
which mixes the Br and Bz components.
Correction for Current Drift
•
•
•
•
Average B-field of 4 NMR probes
used to calculate “actual” solenoid
current.
Scale all measurements to a
reference current (7600 A).
Effect of drift in current removed
Calibration capable of coping with
any sort of drift.
Correction for Hall Probe Drift
• Mapping machine regularly
returns to fixed calibration
positions
– Near coil centre to calibrate Bz
– Near coil end for Br
– No special calibration point for B
• Each channel is calibrated to a
reference time (beginning of run)
• Offsets from calibration points
used to determine offsets for
measurements between
calibrations
Fit Quality with Expected Performance
phi 1
phi 2
0.5
phi 3
phi 4
0.4
phi 5
phi 6
phi 7
0.3
0.2
phi 8
phi 9
Geometrical fit. Error level 5
0.1
phi 10
2.
3
1.
9
1.
5
1.
1
0.
7
0.
3
-1
.7
-1
.3
-0
.9
-0
.5
-0
.1
-2
.5
-2
.1
0
Pseudorapidity
6
-2
Fourier-Bessel fit. Error level 5
-4
2.
3
1.
9
1.
5
1.
1
0.
7
0.
3
phi 5
phi 6
-0
.1
0
-0
.9
-0
.5
phi 3
phi 4
-1
.3
2
-1
.7
phi 1
phi 2
-2
.1
4
-2
.5
Relative sagitta error x 10^4
• Expected mapper
performance
corresponds to error
level 5.
• Both fits accurate
within target level of
5×10-4.
Relative sagitta error x 10^4
0.6
phi 7
phi 8
phi 9
phi 10
-6
Pseudorapidity
Probe normalisation and alignment corrections
Hall probe triplets are accurately perpendicular to each other, but their mounting
on mapper can have ~1 mrad errors.
Hall probe calibration will probably be good to 0.1% but we can improve it by
taking normalisation from the NMR probe at Z=R=0.
We get best results by calculating PNA corrections with a variant of the FourierBessel fit and using the corrected values in the geometrical fit :
30
6
Before probe normalisation and alignment corrections
After probe normalisation and alignment corrections
Before probe normalisation and alignment corrections
After probe normalisation and alignment corrections
20
Mean
Bz error (Gauss)
10
RMS
Max
Min
0
1
2
3
4
5
6
7
8
9
10
Mean
RMS
Max
-10
Min
-20
Relative sagitta error * 10^4
4
Mean
2
RMS
Max
Min
0
1
2
3
4
5
6
7
10
Mean
Max
-2
Min
-6
Ten runs with different random errors
9
RMS
-4
-30
8
Ten runs with different random errors
Field fitting conclusions
• With no simulated errors, both fits have excellent technical
accuracy.
• With realistic simulated errors, both fits give results within
target of 5×10-4.
• Fourier-Bessel fit more sensitive to random measurement
errors:
– Due to more free parameters.
– F-B fit designed for any solenoid-like field, whereas geometrical
fit is specifically for the ATLAS solenoid.
• Probe normalisation & alignment correction from F-B fit
helps significantly.
• Require survey of mapper machine relative to Inner
Detector to be accurate to ~1 mm.
Modified copy of slide from last year
Initial SCT Alignment
X-ray
survey
now
cancelled
I have been promoting the idea making an initial SCT alignment based on
conventional surveys. This is a backup / alternative to the Oxford plan for
an X-ray survey combined with FSI monitoring. The accuracy of the SCT
endcap as built, and as surveyed is now becoming clear
Intrinsic resolution of SCT detector; 22 mm (just under pitch/12).
Detector positions in module; build 4 mm , survey 1 mm (Joe's talk).
Location holes in module; build 10 mm , survey 3 mm.
Module mounting pins on disc; build 100 mm , survey 10 mm.
Discs in support cylinder; build 200 mm , survey 100 mm.
Hole to pin clearance; <10 mm .
Stability of mounting pins on disc; 20 - 50 mm . (temperature, moisture,bending )
7 microns random + 50 microns systematic (proportional to distance)
SCT endcap alignment from surveys
Module internal alignment
Relative positions of the four
detectors and two mounting
holes.
Corrections of ~5 mm known to
~1 mm.
Module production database
Completed July 05
Understand and correct for small
(1-2 um) systematic differences
between surveys done at different
sites.
Pin alignment
Disc alignment
Relative positions of the module
mounting pins on discs.
Relative positions of the 9 discs
in each endcap
Corrections of ~100 um known to
~10 um.
Corrections of ~200 um known to
~100 um.
Tables of pin position offsets
from nominal in each disc.
Survey reports of disc alignment
in each endcap.
Collecting data from surveys done
at Liverpool (Peter Sutcliffe) and
NIKHEF (Patrick Werneke).
First few reports available from
endcap C.
Steve Snow. Endcap C complete,
endcap A discs 9,8,7,6,5,4 done.
Surveys should be repeated when
the endcaps reach CERN.
Steve Snow. In progress.
Joe Foster. In progress.
Corrected final module data.
Joe Foster. Expected Jan 06
Tables associating module serial number
with position mounted on disc.
Joe Foster. Endcap C complete. Endcap A
expected December 05.
combine
Detector/module
offsets from nominal
in each disc.
Steve Snow, Joe
Foster.
Expected March 06.
Detector/module
offsets from nominal
in each endcap.
Steve Snow, Joe Foster.
Expected
May 06.
Learn how to load data into, and use data
from, the conditions database. Upload this ?
or this ? data
Paul Miyagawa. Expected July 06.
Disc surveys
Survey of module mounting pins on all endcap C (UK) discs is complete.
150
Overlap statistics
Overlap (microns)
100
50
0
1
2
3
4
5
-50
-100
6
7
8
9
O-rms
O-max
O-min
M-rms
M-max
M-min
I-rms
I-max
I-min
O-tol
M-tol
I-tol
O-tol
M-tol
I-tol
-150
Disc number
Actual phi overlap between neighbouring modules will always be within 120
microns of the design value, and typically within 50 microns.
Strip pitch is 80 microns, design overlap is 5,8,18 strips. (I,M,O rings)
There will always be a small but useful overlap between modules to use for
alignment with tracks.
NMR system
• Purpose and description of the NMR
• Overview of system
• Parts of the system
• Software for:
Noise tests
Signal tests
• Installation and Commissioning
• Configuration during field mapping
Steve Snow
26/10/05
Technical support
in Manchester:
Julian Freestone,
Mike Perry
CERN contact:
Pippa Wells
Overview
Aim is to measure the magnetic field strength in the Inner Detector.
NMR requires a very uniform field (<250 ppm/cm) so we must place the
probes at z=0. Extrapolation to other parts of the Inner Detector relies
increasingly on the field map as one moves towards the end-caps.
NMR is intrinsically accurate; it it works at all we get a result accurate
within a few x 10 ppm.
Based on a system supplied by Metrolab, with modifications to improve
radiation hardness of the probe and cables.
Operating at/beyond the limits of some specifications:
• expected field gradient is 310 ppm/cm
• probe-amp cable length is 15m, Metrolab standard is 7m
• amp-readout cable length is 125m, standard is up to 100m
Metrolab say their specifications are conservative and this should be no problem.
NMR
system
Standard Metrolab
system with the
addition of Pico
2-channel digitiser
and PC to monitor
noise, pickup,
signal size, etc.
Grounded only at
ID ground point.
Readout using
LabVIEW on PC.
Interface to DCS
not yet defined.
Parts of the system
All of the hardware is ready.
Some software still being developed.
Probe in
clamp on
cryostat wall
Probe
Amplifier
Readout
Cables
Noise Tests
The only thing likely to prevent the NMR
system from working is noise pickup.
In lab, pickup depends strongly on layout of cables ; as soon as cables are laid
in Atlas we want to measure noise and check it is not excessive.
Maybe an opportunity to immediately re-route or bundle cables more tightly together. Final
test is the ability to lock onto the NMR resonance - not possible until much later, when
solenoid is turned on.
NoiseTest.VI - automates all
the NMR tests we can do in
absence of field.
100
80
60
40
Noise (mV)
r.m.s.
Max
20
Min
0
50 Hz
28
38
48
58
68
78
88
-20
100 Hz
150 Hz
200 Hz
-40
-60
-80
-100
Frequency (MHz)
Noise test results in good conditions:
r.m.s. ~ 20 mV, peaks < 100 mV
mains pickup < random noise
Signal Tests
When the Teslameter is locked on the NMR resonance, as well as reading out the
field value we monitor peak height, peak asymmetry and noise (between peaks).
SignalTest.VI
Mapping time scale
Latest ATLAS schedule shows mapping in April/May.
We will prepare for that date but I would be surprised if it
does not slip by 2 or 3 months.
Looking forward
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
2006
Field map
NMR
Survey alignment
Track alignment
SuperNEMO
2007
My changing priorities in the next year.
Seminars
11/01/06
18/01/06
25/01/06
01/02/06
08/02/06
15/02/06
22/02/06
01/03/06
08/03/06
15/03/06
22/03/06
29/03/06
30/03/06
05/04/06
Experiment
Theory
Schuster
Experiment
Experiment
Theory
Schuster
Experiment
Theory
Experiment
Experiment
Experiment
Schuster
Brian Fulton (York)
COBRA
Yoshi Uchida (Imperial)
Tara Shears
KamLAND
LHCb
Amanda Cooper-Sarkar
Chris Booth
Alfons Weber
Emily Nurse
MICE
MINOS
CDF
Not yet fixed:
Martin Erdmann - Auger,
Dino Jaroszynski - plasma acceleration.