S. Claudet (CERN, Geneva) on behalf of the “Cryogenics Group”
Technology Department
Workshop Accelerator Operation 2012, SLAC

Outline
• Introduction to LHC Cryogenics
• Operation, organisation and results
• Availability and interaction with beam operations
• Summary
Workshop Accelerator Operation 2012, SLAC 2/30 LHC Cryogenics, interface with beam operation

p-p collision 10 34 cm -2 .s
-1 , 14 TeV, 0.5 GJ stored energy
Machine operation
Technology
24 km of superconducting magnets @1.8 K, 8.33 T
Workshop Accelerator Operation 2012, SLAC 3/30 LHC Cryogenics, interface with beam operation

P t 5
P t 4 P t 6
8 x 18kW @ 4.5 K
1’800 sc magnets
P t 3
P t 7
LHC cryogenics is the largest, the longest and the most complex cryogenic system worldwide
Workshop Accelerator Operation 2012, SLAC
130 t He inventory
P t 2
Magnets
Distribution
P t 8
C r yogeni c pl ant
P t 1. 8 P t 1
4/30 LHC Cryogenics, interface with beam operation

180
160
LHC, ATLAS, CMS
LHC
140
120
Before LHC: existing experience for design, safety, controls, operation, availability, …
100
LEP2+
80
ITER
LEP2
60
40
20
OMEGA,
BEBC,
ISR Low-Beta
ALEPH,
DELPHI,
LEP Low-Beta
0
Tevatron, RHIC, Jlab,
SNS, HERA, Tristan, …
1960 1970 1980 1990 2000
Year We did not start from scratch!
Workshop Accelerator Operation 2012, SLAC 5/30 LHC Cryogenics, interface with beam operation

4.2MW input power
Bldg: 15m x 25m
Oil/Helium Coolers
Workshop Accelerator Operation 2012, SLAC
Compressors
6/30
Motors
LHC Cryogenics, interface with beam operation

18 kW @ 4.5 K Refrigerators (x8)
33 kW @ 50 K to 75 K - 23 kW @ 4.6 K to 20 K - 41 g/s liquefaction
LHe: 3’600 l/h
4m diam, 20m long, 100tons
Workshop Accelerator Operation 2012, SLAC 7/30 LHC Cryogenics, interface with beam operation

1.8K Units with cold compressors (x8)
Active magnetic bearings
Outlet
Pressure ratio
2 to 4
Inlet
Cold Compressor
3-phase induction
Electrical motor
(rotational speed:
200 to 800 Hz)
Fixed-vane diffuser
Spiral volute
Axial-centrifugal
Impeller (3D)
125 g/s GHe from 15 mbar to P atm with 3 or 4 stages
Workshop Accelerator Operation 2012, SLAC 8/30 LHC Cryogenics, interface with beam operation

Electrical feed boxes for current leads
48 Boxes, 1200 leads
LSSL2 of the LHC
Workshop Accelerator Operation 2012, SLAC 9/30 LHC Cryogenics, interface with beam operation

One LHC sector: production-distribution-magnets
Total for 8 sectors:
Compressors: 64
Turbines: 74
Cold Comp.: 28
Leads: 1’200
I/O signals: 60’000
PID loops: 4’000
• Extremely large installed cooling capacity
• Complexity associated with 1.8K units
• Extremely large distribution system
=> Recovery from failures can last from few minutes to 20 hrs, exceptionally 2-3 days x 13.5
From LHC Magnet String test
Workshop Accelerator Operation 2012, SLAC
3.3km
10/30 LHC Cryogenics, interface with beam operation

Voltage change
[%]
Interfaces: follow-up electrical perturbations
EL perturbations and their impact on our LHC Cryo system
Electrical systems recover in ms
Cooling systems recover in min
Cryo systems recover in hrs
=> A big incentive to be as tolerante to glitches as possible
Duration
[ms]
Workshop Accelerator Operation 2012, SLAC
Typical tolerance envelope
11/30 LHC Cryogenics, interface with beam operation

For accelerators in high energy physics
• Compactness through higher fields
E beam
[Gev]
≈ 0.3 . B . r
[T] [m]
E beam
[Gev]
≈ E . L
[MV/m] [m]
Be sure that at design stage, working at higher temperature was considered, but not selected to maximise LHC beam energy
=> Cryogenic systems takes longer to recover from failures than conventional ones (but we work on it!)
• Saving operating energy
Electromagnets:
Resistive: P input
Superconducting: P input
≈ E beam
≈ Pref
Acceleration cavities
P input
R s
≈ Rs.L.E
≈ R
BCS
+ R o
2 /w
R
BCS
≈ (1/T) exp(-BT c
/T)
Workshop Accelerator Operation 2012, SLAC 12/30 LHC Cryogenics, interface with beam operation

Powering OK or interlock
Static and Dynamic heat loads
Workshop Accelerator Operation 2012, SLAC
Beam related
Dynamic heat loads
13/30 LHC Cryogenics, interface with beam operation

Outline
• Introduction to LHC Cryogenics
• Operation, organisation and results
• Availability and interaction with beam operations
• Summary
Workshop Accelerator Operation 2012, SLAC 14/30 LHC Cryogenics, interface with beam operation

• Equipment architecture:
– Central liquefier to intermediate buffer, distribution decoupled
– Cooling capacity production in line with demands
On-call adapted
• Type of operation
– Transients (cool-down / warm-up) or various recovery
– Alarm monitoring, simple reset actions, calling for experts
– Detection of process degradation and curing action
– HW checks and preventive treatment of slow evolving problems
• Frequency of required actions:
– Once per month, once per week
– Once per 1-2 days
LHC: A huge and complex system without significant buffer and frequent operator actions required
Dedicated 24/7 required so far !!!
Workshop Accelerator Operation 2012, SLAC 15/30 LHC Cryogenics, interface with beam operation

Management
Coordinations:
• Team Leaders + Management (1/wk)
• Performance panel (1/2wks)
• Operation / Maintenance panel
• Methods & Tools panel
Tools (web interface DB oracle):
• e-logboog operation for any change of configuration (wanted or not) or observation and diagnostic request
• Diagnostic tables, work-orders, intervention reports
• Asset & spares management, intervention procedures
• Maintenance plan
• Scheduling
Workshop Accelerator Operation 2012, SLAC 16/30 LHC Cryogenics, interface with beam operation

People should be able to quit, newcomers should be integrated
• High level requirements for recruitment (Bachelor & Masters)
• Formalised induction process:
Academic training - On the job training - Shadow shifts
=> Certification after ≈ 10 months as shift operator (alone!)
• Senior operator (>3 yrs):
Able with all sub-systems, ability to optimise production-needs-time
• Certification diploma:
Written - Site - Simulator - Improvement study (report + presentation)
• If selected for indefinite contract:
– Operation for 5 to 10 years
– Ability to become “production Eng.” as site responsible
– Ability to switch to support teams or another activity at Cern
Workshop Accelerator Operation 2012, SLAC 17/30 LHC Cryogenics, interface with beam operation

Cryo operator in Cern Central Control room
Shift 24/7
Fixed displays
Tendancy curves (summary)
Process synoptics and orders
Workshop Accelerator Operation 2012, SLAC 18/30 LHC Cryogenics, interface with beam operation

Alarms Powering
Global availability
Workshop Accelerator Operation 2012, SLAC 19/30 LHC Cryogenics, interface with beam operation

Outline
• Introduction to LHC Cryogenics
• Operation, organisation and results
• Availability and interaction with beam operations
• Summary
Workshop Accelerator Operation 2012, SLAC 20/30 LHC Cryogenics, interface with beam operation

Availability: a signal Yes/No is required
T2 = Achieved up time during required time / Required time x 100 (operational availability)
CM
CS
Cryo Maintain: Few important conditions checking integrity of HW, with slow power abort in case this signal is lost (leading to beam dump !)
SP set-point
CS
CM
Cryo Start: set of conditions to allow powering of concerned sub-sector, with no action if powering started (illustrates good stability of process)
T2 indicator w.r.t
EN 15341
CM
CS CM
Sum CM 8 sectors:
Global availability
Possibility to treat thousands of channels in a structured way to match at best the LHC powering sub-sectorisation and the cryo sub-sectorisation
Workshop Accelerator Operation 2012, SLAC 21/30 LHC Cryogenics, interface with beam operation

2011
2010
2009
100
90
80
Target 2012
95%
70
60
50
40
30
20
L7
TT891
2xP8
CCs
P18 oil ice
P4
CCs
- Excellent 1st part to TechSTop
- Heavy works done during
Technical Stop #1, and cabling weakness caused difficult recovery
- Very moderate impact from High
Luminosity operation in 2012
10
SEU?
P8+R5
0
27-Feb 26-Mar 23-Apr
Scheduled Stops
21-May 18-Jun
Daily 2012
16-Jul
Weekly 2012
13-Aug 10-Sep 8-Oct
Between TS 2012
5-Nov 3-Dec
Workshop Accelerator Operation 2012, SLAC 22/30 LHC Cryogenics, interface with beam operation

100
98
96
94
92
90
88
86
LHCCryo - Average of 8 sectors
(Between TS)
0.5
Global availability as seen by LHC during beam operation periods
2.66
3.51
3.5
Others according to relative ratio of their average for the 8 sectors
5.21
0.66
91.47
4.20
2.46
0.15
89.68
94.5
Supply (EL, CV, IT)
Cryo
Cryo SEU
Users
Global availability
2010 2011
(260 days) (271 days) (137/290)
(Full days, Mondays & Fridays of
Technical Stops not counted here)
Evolution:
- 2010: Correcting early Cryo bugs
- 2011: Adapting to SEU (corrected @Xmas)
- 2012: So far rewarding !!!
Workshop Accelerator Operation 2012, SLAC 23/30 LHC Cryogenics, interface with beam operation

Considering 8 independent sectors
2010-2011
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
50% 60% 70% 80% 90% 100%
Workshop Accelerator Operation 2012, SLAC 24/30 LHC Cryogenics, interface with beam operation

Indicators: recovery categories & tendency
Nb stops
150
125
100
75
50
+ Better global control/tuning
(operation, instrumentation)
- ! SEU !
• Less Cryo induced failures,
. (but 3 VERY LONG ones!)
- More Supply (EL) failures
- ! SEU !
+ No longer recurrent Cold
Compressors particular issues
(Leaks, electronics)
25
Cryo SEU
Cryo down
0
2010 2011 short(<8h)
From the books:
Immediate effect of
(good!) practice
Workshop Accelerator Operation 2012, SLAC
2010 2011
Medium(8h-30h)
Annoying if frequent, to be kept low with moderate efforts
2010 2011
Long (>30h)
Serious cases requiring specific monitoring and significant efforts
25/30
Nice tendency, promising for
2012 or new surprises to come up?
LHC Cryogenics, interface with beam operation

• 2007/2008 cool-down & HWC: Control rooms: site - CCC- office
Per site, one experienced engineer with agreed minimum protocol to guide a local team of operators, with help of support teams (instrumentation, experts, controls)
• Since 2009 and operation with beam:
One operator in shift 24h/7d, more transverse structure site/CernControlCenter, procedures & operation tools
• For machine controls (temperature, level, pressure):
Basic interlocks and simple PID loops with generic tools for fast orders, now completed with automated sequences & procedures
• Indicators:
From temperature stability to daily availability on-line cool-down curves to on-line cryo-status
Workshop Accelerator Operation 2012, SLAC 26/30 LHC Cryogenics, interface with beam operation

Power Consumption for LHC Cryogenics
45
40
35
30
25
Installed power
Stop
Cryoplant
Tests
Operation with 8 plants
Net gain ≈ 50 GW.h per year
(3 MCHF / year !!!)
Cryo optimized power
Gain
≈ 8MW
(20% of installed power)
20
15
10
Cool down
5
0
03-Jul-
2009
HWC
2009
01-Jan-
2010
02-Apr-
2010
Cryo unavailability breakdown
Workshop Accelerator Operation 2012, SLAC
LHC physics
6200 h
91% Cryo Availability
LHC physics
6500 h
90% Cryo Availability
2010
1
3 5
01-Oct-
2010
31-Dec01-Apr-
Cryo
2010 2011
Cryo
2011
Utilities
3
Utilities
Users or Beam
3
Users or Beam
4
27/30
30-Sep-
2011
Cryo
Utilities
Users or Beam
LHC Cryogenics, interface with beam operation

145
143
141
139
137
135
133
131
129
127
125
123
121
119
117
115
159
157
155
153
151
149
147 en tonne
Total masse He 2012 Livraison camion He
TS1 -0.65 T
Remplissage DEWAR Transfert SM18 Transfert CAST Transfert CMS
6
Technical Stop
• Now < 30kg/day en tonne
5
• With 50kg/day in 2011 and better control @Xmas, tendency to be confirmed
4
• @50 CHF/kg 3
- 50kg/day # 2’500 CHF/day
- 150 t # 7.5 MCHF
45
2
40
35
30
25
20
15
10
5
0
Xmas
Tech Stop
Operation
1
0
-1
2010 2011
-2
Workshop Accelerator Operation 2012, SLAC 28/30 LHC Cryogenics, interface with beam operation

• HW signals:
– Cryo Start and Cryo Maintain towards Powering Interlock module
• SW panels:
– Cryo web page
• People in Control Room (LHC):
– 1 Eng in charge + 1 operator
– 1 Cryo operator
– 1 operator for technical infrastructure
Text zone
• Possible evolutions ?
– Closer discussions with Eng. In charge in case of cryo problem
– Other operators involved to help diagnostics/recovery
– No longer cryo operators at night (on call only)
Workshop Accelerator Operation 2012, SLAC 29/30 LHC Cryogenics, interface with beam operation

• LHC cryogenics is the largest, the longest and the most complex cryogenic system worldwide. We could achieve a reasonable availablity
(> 90 %) so far with beams.
This demonstrates that there are no big issues in concept, technology or global approach for operation.
• Despite all our efforts, we had very hard time and lengthy commissioning to learn how to tune all these sub-systems together while permanently consolidating what was not conform. Experience has been converted into automatism, procedures, tools, training
• Cryogenics operation is well integrated in central control room with LHC main systems, but operated/supported independently (about 50 people)
• Maintenance is as well reaching an efficient preventive/corrective ratio, with efforts to be made for non-standard cases. We have to prepare for higher energies and intensities with continued gain in reliability !
Workshop Accelerator Operation 2012, SLAC 30/30 LHC Cryogenics, interface with beam operation