1. 3/10/20071 CNGS Operation Part 1 : CNGS beam operation. Protons on their way to the target. CNGS specialties. Part 2 : Extraction Interlock System. Detailed description. J. Wenninger Acknowledgments : Edda, Verena, Konrad … for figures, photos and numbers.

2. CNGS ‘Facility’ 3/10/20072 A dedicated primary beam line (TT41), a target chamber (target T40), a decay tube & a muon detection infrastructure. ‘Attached’ to the LSS4/East extraction channel.

3. CNGS Tunnels 3/10/20073

4. 4

5. Our Goals 3/10/20075 Send 4.8x10 13 protons to target in every CNGC cycle  Tune, tune, tune … Keep the beam within +- 0.5 mm of the target axis to prevent damage !  Interlocks, interlocks, interlocks…

6. 3/10/20076 CNGS Magnetic Cycle The CNGS beam magnetic cycle is almost identical to the FT beam: the only difference is the much shorter 400 GeV flat top – only 90 ms: 2 fast extractions are programmed 20 ms and 70 ms from the start of the flat top. Time (ms) P (GeV/c) Injections at 0 and 1200 ms. Ramp from 1260 to 4200 ms. Flat top from 4200 to 4290 ms. Cycle length 6 s – 5 BPs. Same optics and tunes than FT beam: Q = (~26.62,~26.58)

7. 3/10/20077 CNGS Beam Longitudinal: 2 batches of ~10.5  s (5/11 of SPS). 2 gaps of ~ 1  s (kickers !). Bunch spacing 5 ns. Bunch length at 400 GeV ~ 2 ns. Transverse: Normalized emittance  *  8-10  m. Beam sizes at 400 GeV (10  m): -Wire scanner 51995  H/V  1.4/0.8 mm -Target T40  H/V  0.5/0.4 mm CNGS beam = FT beam with more intensity, up to 4.8x10 13 p. LHC FBCT Batch 1Batch 2 Kicker gaps

8. LSS4 Fast Extraction Channel 3/10/20078 5 extraction kicker magnets (MKE) operated at 50 kV. 6 septum magnets (MSE), installed on a movable girder. 4 horizontal and 4 vertical bumper magnets: - Horizontal extraction bump of 31.1 mm @ monitor BPCE.418 TPSG protection element for the MSE.

9. Extraction Kicker MKE 3/10/20079 Key constraint for the fast extraction : < 0.1% beam loss during extraction !  Radiation in ECX4 + activation of extraction channel This means that : Beam gaps must be VERY clean. MKE settings (delays, kick length) are critical. Beam Kicker Waveform

10. One of the worst failures of the extraction system is to : Kick with too little/high voltage at 400 GeV. Nominal kick significantly below 400 GeV. To protect the extraction channel and line against such failures, the MKE has an internal Beam Energy Tracking System (BETS) that ensures that: The measured energy for CNGS is within ~0.5% of 400 GeV. The momentum aperture of the line is > +- 0.6%. The energy measurement is based on the current of the main dipoles. The measured kicker voltage must be 50 +- 2 kV.  Inhibits the extraction (no kicker fault !) if not OK ! !! The BETS system does not take into account the energy change due to RF frequency/radial position – please do not trim the radial position for Q’ etc measurements on the flat top – or stop the extraction first !! Beam Energy Tracking 3/10/200710

11. MKE Trigger Logic 3/10/200711 1.Extraction – 13 ms : the PFNs (Pulse Forming Networks) are charged provided the extraction interlock system gives the green light. 2.Extraction + 0.8 ms : the MKEs are triggered when the RF pre-pulse arrives provided that : i.The extraction interlock systems gives the green light. ii.The BETS system gives the green light. Extraction interlock permit CNGS BETS LHC BETS PFN voltage -13 ms ~+0.8 ms NB: the +0.8 ms delay wrt ‘nominal’ extraction time is due to delays in the RF prepulse generation !

12. Extraction Septum 3/10/200712 ElementL mag (m) B (T)Kick/mag (mrad) I nom (A)Septum Thickness (mm) Gap Height (mm) MSE2.24~1.52.1~2000017.220 MSE Extraction channel 12

13. LSS4 Extraction BLMs 13 TPSG Septum magnets BLM1BLM2BLM3BLM4BLM5BLM6BLM7BLM8 Beam loss due to a large vertical size or tails appear here, at exit of septum (largest V size). Loss distibution is due to residual beam in the abort gap. ~ 2x10 13 p The LSS4 BLMs are connected to the ring BIS system (and to the dump) because losses can come from the extracted or circulating beam. The interlocks is latched after 3 cycles by SIS! This strategy may have to be refined…

14. MSE BTVs 3/10/200714 Two BTVs (Al/Ti) with step motors are installed at the entrance and at the exit of the MSE. The BTVs are not interlocked, neither by HW nor by SIS (due to old HW/SW of the step motors). When the BTVs are IN, there can be large losses !! OUT position

15. Compare with LSS2… 3/10/200715 Peak losses more than 20 times smaller than in LSS2 !! Total loss : ~25-50 mGray versus ~3000 mGray ~ 2x10 13 p ~ 2.5x10 13 p

16. RF & Kickers Tuning for clean gaps! 3/10/200716 Constant Voltage 0.9MVThe voltage is ramped up to ~1.3-1.4 MV after injection to minimize beam in the gaps ! An alternative method to clean the gap is to advance the second kick of the injection kicker a bit. Necessary if it does not work with the RF …. Used yesterday !!

17. TT41 Transfer Line 3/10/200717 ~720 m long, 837 m if TT40 is included (from MSE). A string of 8 dipoles (MBSG, RBI.410010) is used to bend the beam towards CNGS. For LHC operation the MBSG is at 0 current. The lattice is basically the same as for the SPS (betatron & dispersion functions). Final focus at the end to reduce beam size on target. Aperture for the beam : > +- 20 mm in H/V.

18. Main Bends Powering 3/10/200718 Interlock DCCTs MUGEF for ‘standard’ surveillance The TT41 and TI8 main dipoles are powered by a single converter, with switches (mechanical and electronic) to send the current into the correct magnet string. The mechanical switches are interlocked with the access chains. To run CNGS when TI8 is in access (like now !), the TI8 (load) switch must be to Earth. If that is not the case, there will be an access interlock on the PC ! To control the switches – use the PC expert (Labview) program ! To ensure that the switch position is correct, there are 2 ‘dummy’ ROCS channels that have only an interlock DCCT but no converter. The names of the ROCS are DCCT_TI8 and DCCT_CNGS (also accessible from equipstate). The 2 DCCTs are used to identify which branch is powered, and their current is interlocked like any other converter. Mechanical swicthes

19. Beam Position Monitors TT40/41 3/10/200719 23 H+V position monitors are installed in TT40 & TT41: 18 button monitors (TT41). 5 couplers: 4 in TT40, 1 in front of T40 (on the target table). Self-triggered electronics: No gain, but a variable integration window (0.4 or 8  s). Default integration window for regular operation is 8  s. At low intensity there can be triggering problems…

20. Steering TT40/TT41 3/10/200720 Steering in TT40/41 is rather easy and reliable (MICADO 1-3 correctors). The line is very stable and requires very little steering. The positions are interlocked, always steer towards the REFERENCE trajectory (beam-target alignment) ! The interlock margin on correctors is +- 10  rad. +- 4 mm +- 2 mm +- 0.5 mm Tolerances : (changes are possible) Those offsets are ‘normal’ : TL-target (mis) alignment !!

21. TT40/TT41 BLMs 3/10/200721 There should be ~no losses in the transfer lines  very low thresholds. The TT41 thresholds are 5 mGray (compare to 50-200 mGray in ring). We may potentially reduce them further by a factor 2 or so. Tbc. BLMs around the TED have higher thresholds to avoid false interlocks when the beam is dumped on the TED. TT40 TT40 TED TT41 Collimator in front of T40 TI8 – not relevant… After target, not interlocked !! ~ 2.5x10 13 p

22. Extraction Timings 3/10/2007 22 CTIMs RF extraction pre-pulses (RF2) The timing must be identical on ALL CNGS users ! Please do not change it - it has consequences on interlocks, logging… Legacy CTIMs

23. Multiple CNGS cycles 3/10/200723 When we run with 3 CNGS cycles mapped to different USERs (CNGS1-3), the ring & TT10 settings may be different for the 3 cycles/USERs. In any case all PC settings will be independent for the 3 cycles. The settings for East Extraction (bumpers, septa), CNGS Transfer (TT40 + TT41), Interlocks … must be (or are by design) identical on all cycles. Any trim must be propagated to all cycles !

24. 3/10/200724 CNGS Secondary Beam 43.4m 100m 1095m18m5m 67m 2.7m TBID / 2 Ionization Chambers Muon Detectors TBID: Target Beam Instrumentation Downstream p + C  (interactions)   , K   (decay in flight)     

25. Extraction Interlocking 3/10/200725 Target Horn

26. 3/10/200726 13 carbon target rods  5 & 4 mm total length 2 m

27. CNGS Muon Monitors 3/10/200727  

28. 3/10/200728 270cm 11.25cm Muon Detectors

29. Muons Profiles 3/10/200729 A fixed display for muon profiles and status of target/horn/reflector/shutter is available. It includes multiplicities and a status word (color) on the quality ! Good Medium Ugly

30. Secondary Beam Control 3/10/200730 The target is not under our control. Horn and reflector are controlled through the working sets. Important : The brilliant SW of the horn/reflector only allows control when a CNGS user is active. Without CNGS user in the SC, one cannot even switch the horn/reflector ON and OFF !!!!!

31. Extraction Interlocking 3/10/200731

32. SIS for TT40 3/10/2007 32 Target BICs Timing inhibit that stops beams with destinations passing through TT40 : CNGS, TI8xx One SIS interlock tree is dedicated to TT40. As usual SIS acts on the BICs and one the timing system. The tree contains the usual stuff (PCs, BTVs, …) but also a surveillance of BLM thresholds (not too high !) and other parameters related to the HW interlock system

33. SIS for TT41 3/10/2007 33 Target BICs Timing inhibit that stops beams with destination CNGS One SIS interlock tree is dedicated to TT41. The tree contains the usual stuff (PCs, BTVs, …) but also a surveillance of BLM and BPM thresholds and other parameters related to the HW interlock system

34. MTG Inhibits 3/10/200734 The SIS signals in the sequence manager (External Conditions)

35. HW Interlock System 3/10/200735 The EAST extraction HW interlock system consists of 7 BIC modules. The hardware is identical to the SPS ring beam interlock system: There 6 ‘slave’ BICs for TT40, TT41 and TI8. There is one MASTER BIC (‘EXT2’). Presently the master BIC just performs an ‘AND’ of the TT40 & TT41 BICs (for CNGS). In the future the master BIC will become ‘intelligent’ in order to handle LHC and CNGS beams in parallel. This requires more signals (‘CNGS’, ‘LHC’) and a more complex logic ! The output signal (‘permit’) of the master BIC is send to the MKE to enable/disable extraction

36. (Un-)maskable Interlocks & Safe Beam Flag 3/10/200736 The HW interlocks may be either UNMASKABLE or MASKABLE. MASKABLE interlocks may be masked when the beam is ‘Safe’. A dedicate signal, the Safe Beam Flag (SBF) is distributed by a timing telegram to the BICs. If the SBF is TRUE, a mask is applied, when it is FALSE the masks are ignored. The SBF is: TRUE if the SPS beam intensity is < 1.3x10 12 protons FALSE if the SPS beam intensity is > 1.3x10 12 protons SBF generation: At the start of every cycle, the SBF is reset to FALSE by the SPS MTG. The intensity measured by the standard SPS hadron BCT (page 1) ~ 1 second after the start of the ramp is send to the SPS MTG. When the MTG receives the intensity from the BCT, it evaluates the SBF and sets it to TRUE is the intensity is < 1.3x10 12 protons. If the BCT-MTG communication fails, the SBF remains FALSE all the time !

37. Interlock (De-)coupling 3/10/200737 Both SW and HW interlock systems act on the MKE and on the (timing) beams with destination CNGS (for SIS), but not on the beam dump and not on the SPS ring HW interlock system.  There is NO coupling with LHC or FT beams !!!

38. HW Interlock ‘Types’ 3/10/200738 For the CNGS fast extractions there are 3 types of interlocks based on : Continuous surveillance of parameters, like (end-)switches. The associated signals change their state rather ‘rarely’. Vacuum, TEDs, target… Pre-extraction surveillance where the interlock signals are evaluated a short time BEFORE extraction. The associated signal is FALSE by default and switches to TRUE for a short time interval around extraction if all conditions are correct. Surveillance of the beam position around extraction point and of the PC currents. Post-extraction surveillance where the interlock signals are (re-)evaluated AFTER extraction. This type of surveillance concerns beam instrumentation. The associated signal is switched to TRUE for a short time around extraction. The interlock signal is latched (FALSE) at the level of the client if a measured beam parameter is out of tolerance. Beam losses and beam positions in the transfer lines. Both Pre- and Post-extraction surveillance tasks are triggered by machine timing events coupled to the main extraction event.

39. ‘Obstacles’ 3/10/200739 Beam ‘obstacles’ that provide inputs to the HW interlock system: Vacuum valves: must be open. TBSE (personnel protection stopper): must be OUT of beam. TED (dump): must be IN-BEAM or OUT of beam (interlock is moving).. Decay tunnel shutter: must be open. Target: must be at a valid position. BTVs: (maskable) Positions : Al, C, Ti, Out. Should be Out by default. Only the Carbon screen is allowed in beam. Al or Ti  interlock ! Interlock when moving. Last screen in front of T40 is locked in beam (C).

40. Misceleanous Inputs 3/10/200740 There are some rather unusual inputs to the Extraction Interlock System: TCC4 Ventilation: interlock is generated if the ventilation system of TCC4 (T40 target chamber) is in ‘Access Mode’. Hadron stop cooling: interlock is generated if the hadron stop (after muons monitors) is not cooled. Fire alarm: A fire detector for TCC4 is also in the chain… …and there is of course the BIG RED INHIBIT BUTTON, in the rack next to the MTG inhibit buttons.

41. Magnets Inputs 3/10/200741 Interlocks related to magnet surveillance: WIC (Warm magnet Interlock Control): magnet temperature surveillance interlock for TT40 and TT41 magnets (one input per TL). MSE girder: this interlock signal combines the following MSE surveillance MSE cooling & temperature. MSE girder : must be in beam, not moving and within +- 2 mm of nominal position. Note that there is NO girder optimization needed for the LSS4 fast extraction. MSE PC must be ON.

42. Powering Failures 42 Powering ‘failures’ are among the most likely and most critical failures : Wrong converted setting  surveillance of the current VALUE. Converter failure  FAST surveillance of the current CHANGE/STATE. TT41 Main Bends Tol. Tolerance Examples of simulated powering failures Tolerance Reaction time ~ 2 ms Reaction time ~ 5 ms

43. ROCS Current Surveillance 3/10/200743 The ROCS system provides a pre-extraction surveillance, the so-called FEI (Fast Extraction Interlock). The current of selected converters has to match a reference within a pre-defined tolerance. The surveillance is performed at the last possible moment ~ 2 milliseconds before extraction. This system provides in total 6 inputs to the BICs, all inputs are MASKABLE: LSS4 bumper converters (H+V) TT41 converters TT40 converters MBI main bend converter MSE.418 converter Interlock DCCTs for shared main converter Operational current tolerances : MBHA, MBHC dipole strings0.2%(RBIH.4100107, RBIH.400309) Main dipole string 0.1%(RBI.410147/RBI.81607) Interlock DCCTs1.0% MBSG dipole string0.1%(RBI.410010) Septum MSE0.1% Main quad strings (D/F)0.2% Matching quads0.5% Corrector magnets10  rad (possible increase to 15  rad) Bumpers1  rad

44. ROCS Surveillance Timing 3/10/200744 For each extraction, the ROCS system provides two 2 ms long pulses when interlock = TRUE which sets a strong constraint on the event sequence (minimizes possible errors). The LEGACY events that trigger the ROCS are: OEX.FINT1-CTMat -13 ms OEX.FINT201-CTMat 0 ms(extraction) 2 ms pulse

45. ROCS Surveillance Diagnostics ‘En attendant FESA…’ 3/10/200745 The software to set thresholds and diagnose the ROCS stuff is still as it was in 2003 - - temporary solution ! I was waiting for the sometimes promised, never delivered FESA version of the ROCS to write some nice(r) application. Diagnostics and tuning is not trivial and I propose for the moment to leave it to the experts: J. Wenninger, M. Jonker and V. Kain. Maybe some training for the supervisors…  Note that the system is very stable and does not need tuning if no trims are made ! The only issue could be (infrequent) steering with correctors!  I could basically re-use the interlock settings from 2006 for all main circuits !! Important: When a ROCS crate is rebooted (m1sba4, m2sba4 or m1sbb4) the FEI settings are lost and must be reloaded – the extractions will be locked. To reload the settings: - Open terminal window (Linux console). - “cd ROCS” - “load_fei_cngs”

46. FMCMs 3/10/200746 The FMCM (Fast Magnet Current Change Monitor) is a device developed at DESY for HERA to detect powering failures on PCs, in particular when the current decay is very fast. The principle of the FMCM is to detect the change in voltage  V when the current decreases rather than to measure directly the change in current  I, because  I/  t is more sensitive when  I and  t are small ! 5 circuits are monitored by FMCMs: L is the circuit inductance CircuitI Nominal (A)Measured  I/I (%) Threshold  I/I (%) Specification for CNGS MSE418200150.120.2 RBIH.4001 (MBHC)6740.030.5 RBIH.4003 (MBHA)8400.010.1 RBI.410010 (MBSG)30860.020.05 RBI.410147 (MBG)39680.010.1

47. FMCM Signal Timing 3/10/200747 Large voltage changes  inhibit Large voltage changes  inhibit FMCM interlock signal The FMCM removes its interlock when the current is stable on the PC flat top. During ramp up/down the large voltage changes  interlock. On the ‘flat bottoms’ the FMCM interlocks because I is too low.  Excellent protection against attempt to extract during the ramp !!!!!!!!!!!

48. Other PC Interlocks 3/10/200748 There are 2 additional PC interlock: Horn and reflector: PC must be ON. MSE Fast internal ‘Sum Fault’: fast internal interlock of the MSE converter. Similar to the SPS MB and MQ interlocks (to BIS in BA3). Very fast signal, delay ~ 1-3 ms.

49. Beam Position in LSS4 3/10/200749 The position of the circulating beam is checked before extraction and interlocked if not within tolerance. The settings are controlled/monitored from the Steering Application (SPSRing), menu Machine Specials. Beware: the position is verified by MOPOS – changing the gain for the first turn may lead to interlocks if the signals are saturated at 400 GeV !!! Interlocked BPM list. Out of tolerance BPMs are highlighted in RED! Interlock settings Measured positions

50. Beam Position in TT40/TT41 3/10/200750 The CNGS beam position interlock settings are controlled from the Steering application (CNGS transfer), menu Machine Specials. The latch status & reset is available from the panel. The interlock settings are not PPM. In a near future, the settings will be controlled via LSA and be part of the Management of Critical Settings (MCS). Any trim will require a NICE login… Guinea pig for the LHC!

51. Post-Mortem for Trajectory 3/10/200751 The Steering application provides a Post-mortem freeze that is activated by default for CNGS: Freezes the display on the last acquisition and changes the DV frame to orange. Stores (internally) the last acquisition with beam. In case the BPM interlock is latched, this provides a display of the last trajectory. To help taking a decision, i.e. reset and continue, or stop and think !

52. Beam Loss Interlocks 3/10/200752 The TL BLMs latch their interlocks. To reset, click there…

53. BI Interlock Timings 3/10/200753 Transfer line BPMs and BLMs LSS4 BPM Latch

54. Standard Supervision 3/10/200754 A supervision application is available for the East Extraction Interlock System. The application is identical to the SPS ring application, and provides the same functionality (masks, status, history buffer…). But there are many very short signals for extraction interlocking, and this application is not so easy to use. Therefore…

55. Extraction Interlock Monitor /1 3/10/200755 To ease the diagnostics of the Extraction Interlock System, I wrote a new application that analyses the signals and produces a simple status, OK or NOT-OK for each cycle. Console manager : ‘SPS Control’  ‘Beam Interlocks’  ‘CNGS Extraction Monitor’. Main screen Index of first faulty channel Interlock signal to MKE, BIC EXT2

56. Extraction Interlock Monitor /2 3/10/200756 BIC detail Time evolution of the signal A tooltip with the channel description should appear is you pass the mouse over the pads.. If the console manager does not interfere ! The green/shadowed regions indicate where the signal must be = 1 (TRUE) to be OK (and to give status = green !

57. Extraction Interlock Monitor /3 3/10/200757 A remote scope is available to monitor PFN charging, BTES and BICs ! Main screen

58. Problems, Known Issues 3/10/200758 TT40/TT41 beam position interlock: So far we have observed a few latched position interlocks, falling into 2 categories. Category A : Fake interlock due to a bad reading on one or more BPMs. Easy to recognize on the difference trajectory (reading that stands out). Occurs after a period without beam, few cycles to days. Reset and everything comes back. Category B : Real interlock, close to the tolerance limit near the targets. Associated to an oscillation that has its source before the line (SPS, extraction channel). Isolated events. Reset and everything comes back to normal. Under investigation… trying to localize the source.  When you encounter a latched BPM interlock, reset it.  If it comes back immediately, stop! Unless it is again category A.

59. ‘Latched Trajectories’ 3/10/200759 Example 1: A real trajectory change. (in H). Under investigations. Large error bars indicate the spread between extraction 1 and 2  possibly due to the second extraction. Example 2: A fake interlock. Only the last monitors show unphysical offsets !  no hesitation : reset ! Both cases : difference wrt reference !

60. Problems, Known Issues 3/10/200760 LSS4 beam position interlock: Main issue is the sensitivity to gain settings. Sometimes the settings must even be modified (systematic changes). SIS for CNGS: SIS is configured to stop the CNGS beam when there is any interlock/abnormal condition in LSS4/TT40/TT41. If you need/want/.. to tune the CNGS beam without extracting, you must mask some of the SIS TT40/TT41 interlocks – or you get no beam. Presently the beam request is stopped by SIS when the extraction is inhibited with the ‘RED BUTTON’. This will be changed tomorrow to be able to stop extraction safely without stopping the beam. Interlock settings: All BLM, BPM interlocks settings are password protected to avoid unintentional changes. I will not show them here because I don’t want then visible on the WEB! The CNGS beam position interlocks will soon be part of the Management of Critical Settings: must be registered to trim/change settings – on the basis of the NICE login. For BLMs small adjustments can be made without problem. For BPMs things are more delicate…

61. It’s all there… 3/10/200761 Detailed system description Test documents & system status Settings references Trouble-shooting Sample screen shots for important information OP programs and diagnostics … For use by the expert and by OP crews ! https://cern.ch/sps-mp-operation/