Update on the PSB Transfer Lines C. Hessler LIU-PSB Working Group Meeting, 18.07.2017

Overview In J.-M. Lacroix’s presentation in LIU-PSB meeting on 11.4.2017 several interferences of elements were reported. Meeting on LIU-PS injection instrumentation (26.4.2017) to clarify needed BPMs (Minutes: https://indico.cern.ch/event/635132/attachments/1449891/2236301/LIU_ PSinjInstrumentation_26Apr17.pdf). LIU-PS injection region instrumentation meeting (24.5.2017) to clarify PS injection wire grid downstream of SMH42 (Minutes: https://indico.cern.ch/event/638159/attachments/1465207/2271491/LIU_ PSinjInstrumentation_24May17.pdf). Several discrepancies between positions and lengths of elements stored in the MAD-X survey file of the current BT/BTP beam line and Geode have been discovered. → Dedicated meeting on 13.7.2017.

Interference between BT.QNO40 and BT.BPM40 J.-M. Lacroix’s presentation in LIU-PSB meeting on 11.4.2017: Solved by moving BPM 150 mm downstream. 150 mm

Position of BTP.VVS10 and BTP.STP10 Different position in the LIU MAD-X file and the 3D scan survey data: Solved by moving beam stopper and valve 49.246 mm upstream. Now the position in the MAD-X file should coincide with the actual position. 49.246 mm

Missing elements BTP.BPMW15 inserted between BTP.QNO30 and BTP.QNO35 at position provided by T. Dobers BTP.BCT10 inserted at position given in MAD-X file of present beam line and moved closer to BTP.QNO60 to avoid interferences with BTP.DVT40. BTP.VVS20 inserted between BTP.QNO60 and BTP.DHZ40. BTP.BPMW15 BTP.BCT10 BTP.VVS20

BPMs for LIU-PS injection instrumentation New Y chamber for LIU in MU41 was installed during this EYETS. The chamber has a port for a BTV right upstream the septa, however there is no BPM included contrary to the original ideas (→ Meeting 26.4.2017). Solution: The recently installed Y chamber will not be modified. Missing BTP.BPM60 will be installed as close as possible to the Y chamber. It can be in either vacuum sector. BTP.BPM30 will be installed 90 deg upstream of the septum exit, between QN050 and 55. BTP.BPM30 BTP.BPM60

Corrector magnets in shielding wall Inaccessible BTP.DHZ10 and BTP.DVT10 corrector magnets in shielding wall to be replaced by two dual plane “Type 1” corrector magnets to gain more redundancy. According to simulations performed by Jonathan Speed, the magnetic length of “Type 1” corrector magnets seems to be similar to the magnetic length of DHZ and DVT magnets . Magnets have been changed in MAD-X file (center positions stay the same), but magnetic length needs to be cross checked with Antony.

PS injection wire grid downstream of SMH42 Problem: The drawing below shows the circulating beam impacting the grid frame when the injection bump is powered. An important difference wrt present situation is that presently the grids are moved together with the septum, while for LIU they will be downstream the septum tank where the envelope separation is even smaller (~few mm) and they will be mounted in a fixed position wrt machine axis. → This could become a problem because the injection bump can be changed, thus the green envelope overlap even more with the grid. Aim is to operate grid without being damaged by circulating beam with correct measurement of injected beams Technical solutions are under investigation Survey file for beam line is independent from this problem.

Discrepancies of MAD-X and Geode survey data of present BT/BTP line Lengths and center positions of some elements differ in Geode and MAD-X survey file of present beam line, e.g. BTP.STP10 (length and position) Quadrupoles (lengths) BPMs (lengths) KFAs and SMVs (lengths and position) Center position of elements In general in a reasonable agreement on the PS side. However, the elements close to the PS have also a small difference of a few mm (e.g. 6 mm in x for QNO.60), which cannot fully be explained by misalignments. On the PSB site the center positions of the quadrupoles are also in good agreement, but some other elements not. Not clear where the differences come from. Possible explanation: Magnetic vs geometric length of magnets (should be magnetic length in MAD-X and Geode) Measurement including/excluding flanges of non-magnetic elements (should be flange-to-flange in MAD-X and Geode)

Starting point of BT/BTP The starting point (extraction point) is different in BT/BTP MAD-X files and Geode. E.g for BT3: There was a discussion in 2013 about changing the starting point and the values in the MAD-X file are consistent with the proposal from that time. Maybe the discrepancy is related to this change? Start and end points should be defined in layout data base. Starting point should be documented in EDMS document. XCCS (m) YCCS (m) ZCCS (m) bearingCCS (rad) slopeCCS (rad) MAD-X 1880.140597 2090.782267 2433.66 0.449471132 Geode 1879.99883 2090.48839 0.449471258

Coordinate system A non-standard coordinate system has been used for the BT/BTP MAD-X survey files. Normally the MAD-X survey coordinate system and the CCS transform as: Has been corrected. Now the MAD-X file produces output files with MAD-X survey coordinates and CCS coordinates (btx_btp.survey and btx_btp.survey.ccs). CCS          MAD-X survey X -X Y Z Bearing -Theta (Different units in Geode and MAD-X!) Slope Phi TiltZ -GlobalTilt (at “sortie” point)

Conclusion Issues reported in LIU-PSB meeting on 11.4.2017 have been corrected. Changes of BPMs discussed in LIU-PS injection instrumentation meeting on 26.4.2017 have been implemented. Technical solution for wire grid downstream of SMH42 is under investigation. Various discrepancies of MAD-X and Geode survey data of present BT/BTP line have been found. This makes it difficult to judge which information is correct and which not. Two possibilities to solve this issue: Either solve all discrepancies and then produce a consistent MAD-X survey file for LIU (Which time is needed to solve all issues?). Or, since the remaining lifetime of the existing beam line is short, take new MAD-X LIU survey file with the recent corrections and define this as “correct”. In parallel correct other files/databases (Proposed solution). This decision must taken by project management. Ideally all important properties (magnetic length, geometric length) of all elements should be defined in the layout database, and the information in all other sources derived from that.