A year of ATLAS preparation. Steve Snow New Year 2006 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 m W to ~15 MeV 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. What I did last year My ATLAS aims

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 p T ~ 40 GeV over large range of η: –Uncertainty in energy loss negligible. –Concentrate on alignment and B-field. Momentum accuracy depends on ∫ r(r max - r)B z dr : –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. This and following slides copied from Paul Miyagawa's talk at the 2nd ATLAS magnetic field workshop

Field shape. 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 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.

Field Mapping Simulation Field model sampled on a grid of 90 z- positions × 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: Solenoid current, 1 A NMR B-field modulus, 0.1 G Each component of Hall probe B-field, 3 G 3.Drifts by random walk process in each measurement of: Solenoid current, 1 A Each component of Hall probe B-field, 0.1 G 4.Random calibration scale and alignment errors, which are constant for each run: Each component of Hall probe B-field, 0.05% scale Rotation about 3 axes of each Hall probe triplet, 1 mrad 5.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. 6.Each Hall probe triplet has a systematic rotation of 1 mrad about the axis which mixes the B r and B z 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 B z –Near coil end for B r –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 Expected mapper performance corresponds to error level 5. Both fits accurate within target level of 5×10 -4.

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 Fourier- Bessel fit and using the corrected values in the geometrical fit :

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× 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.

Initial SCT Alignment 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  m (just under pitch/  12). Detector positions in module; build 4  m, survey 1  m (Joe's talk). Location holes in module; build 10  m, survey 3  m. Module mounting pins on disc; build 100  m, survey 10  m. Discs in support cylinder; build 200  m, survey 100  m. Hole to pin clearance; <10  m. Stability of mounting pins on disc;  m. (temperature, moisture,bending ) X-ray survey now cancelled Modified copy of slide from last year 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  m known to ~1  m. Pin alignment Relative positions of the module mounting pins on discs. Corrections of ~100 um known to ~10 um. Disc alignment Relative positions of the 9 discs in each endcap Corrections of ~200 um known to ~100 um. Module production database Completed July 05 Understand and correct for small (1-2 um) systematic differences between surveys done at different sites. 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. Tables of pin position offsets from nominal in each disc. Collecting data from surveys done at Liverpool (Peter Sutcliffe) and NIKHEF (Patrick Werneke). Steve Snow. Endcap C complete, endcap A discs 9,8,7,6,5,4 done. Detector/module offsets from nominal in each disc. Steve Snow, Joe Foster. Expected March 06. Survey reports of disc alignment in each endcap. First few reports available from endcap C. Surveys should be repeated when the endcaps reach CERN. Steve Snow. In progress. combine 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. 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 Probe Probe in clamp on cryostat wall Amplifier Readout Cables All of the hardware is ready. Some software still being developed.

Noise Tests 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. Noise test results in good conditions: r.m.s. ~ 20 mV, peaks < 100 mV mains pickup < random noise The only thing likely to prevent the NMR system from working is noise pickup. NoiseTest.VI - automates all the NMR tests we can do in absence of field.

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 My changing priorities in the next year.

Seminars Not yet fixed: Martin Erdmann - Auger,Dino Jaroszynski - plasma acceleration.