TE-MPE-TM 1

Zinour Charifoulline, TE-MPE-PE

05/06/2012

Update on Splice Resistance Measurements at 1.9K

(LHC Main Magnet Circuits)

# Splice protection & monitoring – short intro # Recent general statistics (IPAC’12) # 2012 versus 2011: one suspicious case detected # Comparisons with ELQA measurements (preliminary)

TE-MPE-TM 205/06/2012

nQPS BS (A&B)U_MAG: LSB=1.9µV, Range=±15.9V PtP≈500µV(noise)U_RES: LSB=1.5nV, Range=±12.8mV PtP≈50µV-100µV (noise)5Hz, 50points moving average (10s)2048 channels (x2)

Logging DB

U_RES(t), U_MAG(t)I_MEAS(t)

Mag

net

Mag

net

Bus B

ar

1 2 3

4

nQPS BS: Cold Splice Protection and Measurement

Data Source and Current Statistics I

TE-MPE-TM 305/06/2012

Measurements: 3.5-4TeV Ramps with 1 hour on injection and 1 hour on the topCurrent Statistics: about 610 (2010-2012) resistance tables for the bus bars (interconnects) about 200 tables for the internal splices (magnets)

Data Source and Current Statistics II

Splice Protection:- 2048 LHC Main Magnet interconnections;- about 10300 superconducting joints or splices;- 2x2048 nQPS DQQBS boards (A&B);- U_RES > 500µV (83nΩ@6kA) => EE triggered;- measured voltages are stored to Logging DB (5Hz);

Splice Resistance Monitoring:- long enough 3.5-4TeV ramps are detected and analyzed (in automatic way);- resistances are calculated taking into account only plateaus points and saved to csv-files;- warning message (e-mail and sms) are generated if any bus resistance is more than 20nΩ;- second level of warning if resistance is out of 10 sigma range of last saved statistics (noisy boards detection so far);

Injection ~2h20 hours 3.5-4TeV

nQPS DQQBS: URES = UBUS – CCOMP * UMAG

U_RES: LSB= 1.5nV, Range= ±12.8mV, PtP≈ 50µVU_MAG: LSB= 1.9µV, Range= ±15.9V, PtP≈ 300µV

TE-MPE-TM 405/06/2012

RB: 2010

RQ: 2010

RB: 2010 + 2011

RQ: 2010 + 2011

RB: 2010 + 2011 + 2012

RQ: 2010 + 2011 + 2012

618±61pΩ2 splices

918±97pΩ3 splices

2.81±0.31nΩ8 splices

LHC Main Magnet Bus Bar Segments Resistances

TE-MPE-TM 505/06/2012

2010 2011 2012

Bus Bar Segments B34L4_1 versus Time

<R> = ΣRi·(1/σi)2/ Σ(1/σi)2

Var= Σ(<R> -Ri)2·(1/σi)2/ Σ(1/σi)2

TE-MPE-TM 605/06/2012

Splice Num 5 6 7 8 15 16 17 18 19 20 21 32 All

Segments 8 16 8 728 2 11 2 1 2 12 2 8 800

Splice Num 2 3 4 5 6 All

Segments 368 816 48 15 1 1248

RB Bus Bar Segments

RQ Bus Bar Segments

Since each bus-bar segment contains n splices it is not possible to measure the resistance of an individual splice. However, one can estimate the maximum splice resistance in a segment assuming that the excess is localized in one splice only, so Rspl,max = Rsegment – (n-1) * Rspl,avg, where Rspl,avg is the average splice resistance.

Rspl,avg

RB Bus Bars308±30pΩ

Rspl,avg

RQ Bus Bars*301±33pΩ

Maximum and Average Splice Resistances

* In case of quads the number of splices per segment is corrected due to the specific design of the protection voltage taps .The correction estimated by comparing the resistances of 6 and 8 splice segments is about 2x0.20 nΩ.

TE-MPE-TM 7

LHC Main Magnet bus-bars segment resistancesT = 1.9 K

05/06/2012

Main Magnet Bus Bar Segments Resistances, 2010-2011LHC Main Magnet bus-bars maximum splice resistancesT = 1.9 K

1nΩ

2048 total~30 bus bars > 1.2nΩ10σ for MB3σ for MQ

MB 0.30 ± 0.09nΩMQ 0.30 ± 0.31nΩ

Distribution of maximum splice resistances in RB and RQbus-bar segments

2011: Rspl,max

2010: Rspl,max

±100pΩ

The 30 highest bus-bar splice resistances at the end of 2011 versus the end of 2010.

Presented in IPAC’12https://edms.cern.ch/document/1176353/1

Rspl,max = Rsegment – (n-1) * Rspl,avg

TE-MPE-TM 8

RB: 305±77pΩ3σ=0.5nΩ (53)10σ=1.1nΩ (3)

05/06/2012

RQ*: 303±307pΩ3σ=1.2nΩ (24)

LS1 Quality Assurance open questions

-What will be the criterion to remake a cold splice?

- If it is a simple threshold like 1.2nΩ, which is 3Ω for quads, what about dipole distribution tale? They are safe?

- What is a nature of the left part of distributions?- Is it measurement error or there is a “platinum” category of joints?

Thanks to Higgs we have additional 2-3 months to answer. Any ideas welcome.

TE-MPE-TM 905/06/2012

LHC Main Magnet Bus Bar Segments Resistances, 2012

2012

2012

2011

2011

RB

RQ

±200pΩ

±200pΩ

Dipole Bus Bars:No any significant changes of 1248segment resistances are observed.

Quad Bus Bars:No significant changes of 800segment resistances are observed,but except one!B18R2_4: 2.7nΩ -> 4.2nΩ (+1.5nΩ!)B18R2_3: 4.2nΩ since 2010?!Is it “artificial” or “real degradation”?See in the next slides recent ELQA results.

2011 2012

TE-MPE-TM 1005/06/2012

Bus Bar Segments: ELQA measurements in sector 23

Thanks to ELQA-team for the RQ bus bar resistance measurements in sector 23 during last TS#2, which was additional to the planned magnet resistance measurements. The detailed results will be presented by them later.

3.3±0.1nΩ

Degradation?

TE-MPE-TM 1105/06/2012

2010 2011 2012

2010 2011 2012

Bus Bar Segments RQ.B34R2_3&4: nQPS versus ELQA

3.8±0.3nΩ6.2±0.3nΩ

3.4±0.1nΩ5.8±0.1nΩ

TE-MPE-TM 1205/06/2012

2010 2011 2012

2010 2011 2012

4.4±0.3nΩ4.1±0.3nΩ

Bus Bar Segments RQ.B18R2_3&4: nQPS versus ELQA

TE-MPE-TM 1305/06/2012

Bus Bar Segments RQ.B18R2_3&4

5340A2011

6100A2012

- Compensation was not changed;- Board A and B behave the same;- What else?- Something inside of Cold Mass?- If so, why only in one aperture?

TE-MPE-TM 14

Internal Splices: nQPS versus ELQA

05/06/2012

Error bars:ELQA - about 1nΩ from linear fit;nQPS – distribution width divided by SQR(N),which is about (5-9)nΩ / 15;

Preliminary!

ELQA

nQPS

TE-MPE-TM 1505/06/2012

Thanks!

TE-MPE-TM 1605/06/2012

Additional slides

TE-MPE-TM 1705/06/2012

CH#1

CH#2

CH#4

CH#3

CH#6

CH#5

EE111 EE112 EE113

EE211EE219

EE119

EE213 EE212

EE014EE015EE013EE012

R= 100 W

MBA Left

External BB External BB

CH#7

CH#8

EE014

Giorgio D’AngeloMateusz Bednarek

TE-MPE-TM 1805/06/2012

Giorgio D’AngeloMateusz Bednarek

TE-MPE-TM 1905/06/2012

RQ: 113±26pΩRB: 98±22pΩ