second lhc splice review

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Second LHC Splice Review

Copper Stabilizer Continuity Measurementpossible QC tool for consolidated splices

H. Thiesen 28 November 2011

K. Brodzinski, Z. Charifoulline, G. D’Angelo, M. Koratzinos, J. Steckert,H. Thiesen, A. Verweij

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CSCM possible QC tool for consolidation splices

Outline

• Project motivations and objectives• Tests description• Powering implementation• Circuit protection• Cryogenic issues• Main risks• Planning and impact• Conclusion

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Project motivations and objectives

Recommendation:

(R9) Launch the Copper Stabilizer Continuity Measurements Project aimed at the measurement of all the copper stabilizer joints in all the LHC sectors during the technical stop at the end of 2011. On the basis of these measurements the safe 2012 operation beam energy can then be determined.

Conclusions of Steve Myers from Chamonix 2011: Recommendations of the 3rd MAC meeting:

• The CSCM project was launched after Chamonix 2011 to identify for each main circuits (MB and MQ) the maximum safe current.

• The main objective is a possible increase of energy in 2012.

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t1 t2

500 A

4-6 kA

60 s

PC in voltage mode PC in current mode

Trip by mQPS th

T = 20 K

I_circuit, V_bus

t

• CSCM tests consist to reproduce similar conditions to those during a quench, but w/o energy stored in the magnets so that the thermal runaway can safely be stopped by an interlock process.

• This is achieved by doing the test at a temperature of about 20K, so that the magnets are no longer superconducting and the current passes through the bypass diodes connected to all main magnets.

Test descriptionH

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• During the test the busbar segment voltages are measured to detect the runaway.

• Maximum safe current of the circuit can be calculated with the time delay and the current level.

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time delay

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• The CSCM does not measure the quality of each splice. It can only identify the worst one.

Limitation of CSCM

Cool down

CSCM tests

Runaway

Warm up

repair

OK

no

yes

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current at which the machine will run is larger than the safe current deduced from the CSCM test.

What can the CSCM measure?

• The CSCM can also measure:

• All 13 kA current lead-busbar connections at the DFB

• All bypass diode paths

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Test implementation

• LHC has been designed to operate the main dipole and quadrupole magnets with super fluid helium at 1.9K.

• CSCM requests to operate the main MB and MQ magnets with gaseous helium at 20 K.

• Special cryogenic control to maintain the arc at 20K

• Special powering configuration to inject 6kA in the circuits

• Special protection system to protect the circuits during the powering tests

• The new powering configuration and the circuit protection system have to be designed and commissioned as permanent systems

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Powering configuration

RB circuit RQ circuits (in series)

Open circuit Short circuit Open circuit Short circuit

• The voltage delivered by RB (190V) and RQ (18V) power converters are not enough for the CSCM tests:

• 1.7 < Vdiode < 2 V at 20 K (assumption)

Þ Modification of actual RB power converter to obtain the requested voltage

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• Modification of RB power converter

Normal configuration CSCM configuration

U_out

I_out

Tests in P-Hall with 4 W load

U_bridge

U_out

L

L L

L

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Same modified power converter (RB) for the both circuits (MB and MQs)

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• RB powering configuration

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RB 300 V300V

1x240mm2 1x240mm2

• RQ powering configuration

RQD

RQF

RB300V

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current (A)Vdiode = 0.7 VL = 10 mHVout PC = 0 V

• Main challenge = How to control the current in the “diode circuits” ?• 5 bars have to be maintained in the cryostat to have 400V insulation

voltage at 20K

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CSCM protection system

• During the powering tests, the CSCM protection system have to protect:

• Busbar segments

• Current lead

• Magnets

PC

Current LeadsExisting DQQDC detector(3mV 100ms)

…

BB splice & diode BB -> mDQQBS board

…

Diode/MagnetDQQDS measures voltage over 4 magnets if difference is > threshold, current will be cut

Umag

Ures

Current LeadsExisting DQQDC detector(3mV 100ms)

Global BB detector (monitoring)EE system is bridged

PICInterlock Loop from QPS

EE system bridged

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• Busbar protection system

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Recorded mDQQBS buffer, stimulated with simulated signal for a bad splice

Usplice

dv/dt splice

dv/dt threshold

absolute thresholdramp

plateau

1000 boards are in production and will be delivered in December 2011

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• Tests in SM18

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T5

Conn

ecti

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VT13

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VT12VT6

VT7

VT8

VT9

VT10 VT2 VT11

T1

T2

T3

T4 T6

mBS

VT1-13L=11.4m

I2C/

SPI

mBS, board A

mBS, board B

IMAX=5.1kAdI/dt = 200A/sT = 14.5K

UBUS

dV/dt

The busbar segment protection system has been tested in SM18• 10 m of MQ busbar• 50 mm single-sided defect

Special cryogenic condition

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C1109_11L4_TTAVG.POSST

C11L4_11L4_TTAVG.POSST

















conditioning

stabilization

RRR tests

Homogeneity over a sector length for RRR

• Requested cryogenic conditions can be provided with good stability and homogeneity over a sector length: ARC at 20 K and 5 bars, DFBs cooled with 20 K GHe to maintain the current lead at nominal condition (TT891A@50K)

• Proposed cooling of DFBs have to be analyzed in more in details

• Particularity of busbar interface between DFB/Q7 interface to be studied

• Recovery after each powering test is estimated at 5 hours

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CSCM main risks

• CSCM tests

• During the CSCM tests the main risks (extremely small) are to damage a splice, a diode, a magnet or a DFBA (current leads or splice).

• Splice or diode are “easy” to repair (warm up, repair, cool down, CSCM tests)

• Magnet is “easy” to replace if spare is available (warm up, replace, etc…).

• DFBA is more complex to repair: must be transport to the surface.

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• Recovery

• Important modification have to be done to realize the CSCM tests

• The main risk is to do a mistake during the recovery

• The risk can be mitigate to acceptable level by procedure for reconfiguration, test and (re)commissioning.

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CSCM planning

• CSCM tests request time and resources

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s1 s2

s3 s4

s5 s6

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Brief estimation of time• 2 sectors in parallel• 2 weeks for preparation• 2 weeks for the tests• 2 weeks for the recovery and recommissioning

18 weeks (4.5 months) to tests the LHC

- Planning can be optimized to reduce the time at 3.5 or 2.5 months

- Preparation time can be done in parallel with the other LS1 activities

- But powering tests can be done only during the night- CSCM campaign requests resources: 8 to 10 tech. or

Eng.

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CSCM planning

• If CSCM tests must be realized after the consolidation of the splices:

• The project have to be approved in March - April 2012

• Type test has to be realized in one sector at the beginning of the LS1 (6 weeks)

• CSCM campaign has to be integrated in the LS1

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Conclusion

• CSCM tests can be used to qualify the LHC at 7 TeV after the splice consolidation: qualification of the splices, diode paths and current lead – busbar connections

• CSCM tests require to modify several critical systems as QPS, 13kA-EE, PIC and PC: full re-commissioning (IST and powering tests) is mandatory.

• Cryogenic conditions can be provided with good stability and homogeneity over a sector length but proposed cooling of the DFBs has to be analyzed in details.

• CSCM tests will interfere with other LS1 activities

• CSCM tests present some risks (extremely small): damage a splice or a DFB/CL can not be excluded

• CSCM tests require time (2.5-3.5 months) and resources (8-10 technicians-Engineers)

• Engineering challenges are being met and a test and simulation program is under way (validation of protection system, correlation between 20 K and 1.9 K, control of power converter)

• No show stoppers found so far but there are some open issue as PC current control.

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second lhc splice review

Documents

cscm project

cscm measure

main magnets

maximum safe current

current path

current passes

current level

cscm requests