3/10/2007 1

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.

CNGS ‘Facility’

3/10/2007 2

• 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.

CNGS Tunnels

3/10/2007 3

3/10/2007 4

Our Goals

3/10/2007 5

Send 4.8x1013 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…

3/10/2007 6

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)

3/10/2007 7

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 4.8x1013 p.

LHC FBCT

Batch 1 Batch 2

Kicker gaps

2

*

LSS4 Fast Extraction Channel

3/10/2007 8

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.

Extraction Kicker MKE

3/10/2007 91.E+08

1.E+09

1.E+10

1.E+11

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23time us

p+

0.0

0.2

0.4

0.6

0.8

1.0

1.2 k/k

o

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

• 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

3/10/2007 10

MKE Trigger Logic

3/10/2007 11

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 !

Extraction Septum

3/10/2007 12

Element L mag (m)

B (T) Kick/mag (mrad)

I nom (A) Septum Thickness (mm)

Gap Height (mm)

MSE 2.24 ~1.5 2.1 ~20000 17.2 20

MSEExtractionchannel

12

LSS4 Extraction BLMs

13

TPSG Septum magnets

BLM1 BLM2 BLM3 BLM4 BLM5 BLM6 BLM7 BLM8

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.

~ 2x1013 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…

MSE BTVs

3/10/2007 14

• 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

Compare with LSS2…

3/10/2007 15

• Peak losses more than 20 times smaller than in LSS2 !!

• Total loss : ~25-50 mGray versus ~3000 mGray

~ 2x1013 p ~ 2.5x1013 p

RF & Kickers Tuningfor clean gaps!

3/10/2007 16

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 !!

TT41 Transfer Line

3/10/2007 17

• ~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.

Main Bends Powering

3/10/2007 18

MUGEF

DCCT

Ref.

Cyclestatus

MUGEF

ADC

ADC

Extractionpermit / abort

TI 8Main

Dipoles

CNGSMain

Dipoles

ControlSystem

3 600 V

5 400 Apeak

MB 1 MASTER

MB 2 SLAVE

Firing

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

Beam Position Monitors TT40/41

3/10/2007 19

•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…

Steering TT40/TT41

3/10/2007 20

• 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 mmTolerances :

(changes are possible)

Those offsets are ‘normal’ : TL-target(mis) alignment !!

TT40/TT41 BLMs

3/10/2007 21

• 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

TT40 TED

TT41

Collimator in front of T40

TI8 – not relevant…

After target, not interlocked !!

~ 2.5x1013 p~ 2.5x1013 p

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

Multiple CNGS cycles

3/10/2007 23

• 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 !

3/10/2007 24

CNGS Secondary Beam

43.4m100m

1095m 18m 5m 5m67m

2.7m

TBID / 2 Ionization Chambers Muon DetectorsTBID: Target Beam Instrumentation Downstream

p + C (interactions) , K (decay in flight)

Extraction Interlocking

3/10/2007 25

Target

Horn

3/10/2007 26

13 carbon target rods 5 & 4 mm

total length 2 m

CNGS Muon Monitors

3/10/2007 27

3/10/2007 28

270cm

11.25cm

MuonDetectors

Muons Profiles

3/10/2007 29

• 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

Secondary Beam Control

3/10/2007 30

• 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 !!!!!

Extraction Interlocking

3/10/2007 31

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

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

MTG Inhibits

3/10/2007 34

The SIS signals in the sequence manager (External Conditions)

HW Interlock System

3/10/2007 35

• 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

(Un-)maskable Interlocks & Safe Beam Flag

3/10/2007 36

• 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 < 1.3x1012 protons• FALSE if the SPS beam intensity is > 1.3x1012 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 < 1.3x1012 protons.• If the BCT-MTG communication fails, the SBF remains FALSE all the time !

Interlock (De-)coupling

3/10/2007 37

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 !!!

HW Interlock ‘Types’

3/10/2007 38

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.

‘Obstacles’

3/10/2007 39

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).

Misceleanous Inputs

3/10/2007 40

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.

Magnets Inputs

3/10/2007 41

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.

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

ROCS Current Surveillance

3/10/2007 43

•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 strings 0.2% (RBIH.4100107,

RBIH.400309)

Main dipole string 0.1% (RBI.410147/RBI.81607)

Interlock DCCTs 1.0%

MBSG dipole string 0.1% (RBI.410010)

Septum MSE 0.1%

Main quad strings (D/F) 0.2%

Matching quads 0.5%

Corrector magnets 10 rad (possible increase to 15 rad)

Bumpers 1 rad

ROCS Surveillance Timing

3/10/2007 44

•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-CTM at -13 ms

• OEX.FINT201-CTM at 0 ms (extraction)

2 ms pulse

ROCS Surveillance Diagnostics‘En attendant FESA…’

3/10/2007 45

•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”

FMCMs

3/10/2007 46

• 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:

t

ILV

~ L is the circuit inductance

Circuit I Nominal (A) MeasuredI/I (%)

Threshold

I/I (%)Specification

for CNGSMSE418 20015 0.12 0.2

RBIH.4001 (MBHC) 674 0.03 0.5

RBIH.4003 (MBHA) 840 0.01 0.1

RBI.410010 (MBSG) 3086 0.02 0.05

RBI.410147 (MBG) 3968 0.01 0.1

FMCM Signal Timing

3/10/2007 47

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 !!!!!!!!!!!

Other PC Interlocks

3/10/2007 48

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.

Beam Position in LSS4

3/10/2007 49

• 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

Beam Position in TT40/TT41

3/10/2007 50

• 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!

Post-Mortem for Trajectory

3/10/2007 51

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 !

Beam Loss Interlocks

3/10/2007 52

• The TL BLMs latch their interlocks.

• To reset, click there…

BI Interlock Timings

3/10/2007 53

Transfer lineBPMs and BLMs

LSS4 BPM

Latch

Latch

Standard Supervision

3/10/2007 54

• 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…

Extraction Interlock Monitor /1

3/10/2007 55

• 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

Extraction Interlock Monitor /2

3/10/2007 56

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 !

Extraction Interlock Monitor /3

3/10/2007 57

A remote scope is available to monitor PFN charging, BTES and BICs !

Main screen

Problems, Known Issues

3/10/2007 58

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.

‘Latched Trajectories’

3/10/2007 59

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 !

Problems, Known Issues

3/10/2007 60

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…

It’s all there…

3/10/2007 61

• 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/