A Reichold JAI Oxford for the Li

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Survey and Alignment of the ILC Alignment Errors Warsaw University Li. CAS Linear Collider Alignment & Survey 3/16/2018 1

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Overview n n n The ILC survey and alignment process RTRS measurement principle for the reference survey Simulations of the survey process n Reference survey n n n Stake Out and alignment Interface to Placet Systematic errors in the reference survey Error Reduction n n How accurate can position alignment really be Cryo-module improvements n n n SIMULGEO models for short distance (<100 m) Random walk models for long distance fiducialisation build tolerances Survey and Alignment of non-Linac components n Sources, DR, turnaround, BC, BDS, IP, spectrometer, polarimeter, dumps DESY, Sep. 27, 2005 2

A. Reichold, JAI @ Oxford for the Li. CAS collaboration The ILC survey and alignment process (in the tunnel) 1. Reference survey (the hard part): Stake out: n n n 2. n n n 3. n n s<50 mm any point Alignment: n sstat<200 mm/600 m s<100 mm any point rapidly establish co-ordinates of regular array of reference markers along entire tunnel wall rapid = much faster then drift of tunnel rapid = as fast as possible since time = money hard = keep accuracy over large distance new instrument = RTRS (Rapid Tunnel Reference Surveyor) instrument developed by Li. CAS group Relate external accelerator component’s markers to reference markers measurement distance = across the tunnel diameter manually operated classical instruments could work but should be incorporated into RTRS if possible (speed, automation) adjust position of accelerator element to get closer to nominal no automated process for cryo-modules exist yet manual action with a large wrench needed so far least accurate of steps so far DESY, Sep. 27, 2005 3

A. Reichold, JAI @ Oxford for the Li. CAS collaboration The ILC survey and alignment process (outside the tunnel) 4. Fiducialisation (under development): n n n s≥ 300 mm Relate external markers to relevant active centre line of accelerator element If necessary define an average active centre line if many elements determine the centre line as done in cryo-module Center line may dynamically change during cool down and transport. This is the biggest contribution to the fiducialisation error. 5. Build tolerances: n Internal to an accelerator element there could be n n n static variation of several active elements around the centre line (scatter of cavities in cryo-module) adjusted to s=100 mm dynamic changes of elements with load, current, trim, external temperature, etc. s=? ? ? mm Externally there could be n n variations in target marker position when placing the markers repeatedly into their nests (dirt, dust, wear) s≤ 1 mm marker centring errors (markers are usually sphere mounted to allow for large acceptance angles by repointing. If target not correctly centred in sphere you get an error) s 0. 5 mm DESY, Sep. 27, 2005 4

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Notes about the process n Notation: n n n Some offsets correlate within groups of accelerator elements n n n offset = one instance of statistical quantity called error = sigma of the offset distribution all elements in a cryo-module share the same offset due to stake out and alignment 100% correlation External build tolerances also apply identically to all elements in a module but they are usually negligible The fraction of the fiducialisation error due to cool-down distortions is not the same for all elements but is systematically distributed to the elements some correlation function dependent on module mechanics Offsets from reference survey are strongly correlated over very long distances. I. e. better then 200 mm over 600 m (see simulaions) All other offset sources are uncorrelated over distances > 1 cryomodule length DESY, Sep. 27, 2005 5

A. Reichold, JAI @ Oxford for the Li. CAS collaboration RTRS concept wall markers internal FSI SM beam external FSI Tunnel Wall Li. CAS technology for automated stake-out process Reconstructed tunnel shapes (relative coordinates) collider component DESY, Sep. 27, 2005 6

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Li. CAS Measurement Principle External FSI System measures Wall marker location Internal FSI System Dz. & Dx, Dy & Da, Db between cars Straightness Monitor DESY, Sep. 27, 2005 Dx, Dy & Da, Db between cars 7

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Reference Survey Simulations (short distance < 100 m) n n Build opto-geometric model of all measurements in a 6 -car train and all reference wall markers using SIMULGEO Add up to 20 trains in advancing locations into the model n n Most wall markers get measured 6 times in overlapping measurements this is how trains correlate with each other Perform error propagation: n n model consists of 20 trains measuring 26 wall markers. total of O(10. 000) elements and measurements with individual errors in the model from: position errors of elements in the cars and measurement errors to : errors of wall markers, i. e. invert error matrix of rank N 2 = 10. 0002 Limit of this procedure is memory of computer 20 trains need close to 1 GByte and 34 h on 2 GHz CPU DESY, Sep. 27, 2005 8

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Laser beam parallel to Gravity @ car 1 Simulgeo Model of RTRS only first and last car of 6 -car train shown Laser beam parallel to Gravity @ car 6 1 st CCD faking clinometer LSM-CCDs for return beam wall marker internal FSI lines intermediate cars not shown retro reflector straightness monitor laser beam LSM-CCDs for incoming beam DESY, Sep. 27, 2005 2 nd CCD faking clinometer 9

Reference Survey Simulations (long distance >100 m) 10

A. Reichold, JAI @ Oxford for the Li. CAS collaboration DESY, Sep. 27, 2005 11

A. Reichold, JAI @ Oxford for the Li. CAS collaboration DESY, Sep. 27, 2005 12

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Stake out and Alignment Simulations n n Both processes so far only add a Gaussian random offset to the reference survey Width of these Gaussians is so far based on separate instrument errors and error propagation by surveyors. n n Assumptions: shoriz=0. 3 mgon, svert=0. 3 mgon, sdist=0. 1 mm, DL between reference markers = 5 m, Note: 1 gon = 2 p/100, 1 mgon = 63 mrad In future we will fully simulate an integrated stake out with SIMULGEO and determine the errors to see if we can decrease them. DESY, Sep. 27, 2005 13

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Interface to Placet (licas_sim) n n n Fortran program tested on Linux licas_sim produces the offsets of components given their z positions All internal tuning parameters (measurement resolutions) are in a control card file and can be modified by users Input: two flat text files (one for each arm of the machine) with one z position per line, representing the nominal z of the component to be aligned. Output: each line of input replaced with: n n z-original, x-offset, y-offset, z-offset All units are meters DESY, Sep. 27, 2005 14

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Systematic errors in reference survey n n We have no measure of them yet Hard to measure because Li. CAS “would” be the highest accuracy instrument Mainly to be determined via consistency checks during Li. CAS test runs at DESY next year Potential sources of systematics exists in: n n n miscalibration of components (predominant source) scale-mismatch between sub-systems drift errors on precision components systematic atmospheric effects Most of them would be addressed by calibration procedures Which systematic errors would be dangerous for LET? DESY, Sep. 27, 2005 15

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Error Reduction n Position Alignment: n Today’s movers for cryo-modules n n manual coarse movers (lots of force needed) few cm range hardened steel feet on hardened steel plate If the estimated 100 mm accuracy prove to be insufficient and money is available one can: n n n Mount modules using bearings motorise adjusters achieve O(10 microns) DESY, Sep. 27, 2005 16

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Error Reduction n Cryo-module fiducialisation n n 300 microns is limit with current module design better is possible but at great cost part of 300 microns is currently uncertainty rather then error. I. e. expected scatter of beam line positions in a large number of modules. if you measure each one of them internally (wire system) you can get better transport and handling is a large unknown factor DESY, Sep. 27, 2005 17

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Error Reduction n Cryo-Module build tolerances n n n scatter of cavities in a string = 100 mm < fiducialisation error no need to improve offset of quads from beam line = 100 mm This is currently not the leading error DESY, Sep. 27, 2005 18

A. Reichold, JAI @ Oxford for the Li. CAS collaboration Survey and Alignment of non-Linac components n n We know neither specs nor methods yet We are working on a document to collect these Would be very useful to prioritise the list by knowing which part is most sensitive Input from WG 1 of highest importance DESY, Sep. 27, 2005 19