LHC Collimators Low Level Control System

LHC Collimators Low Level Control System Dr. A. Masi CERN, Switzerland AB Dept, ATB group [email protected]

Outline

• • • • • • • •

The LHC collimation system Control requirements Control system layout The RT platform used Control system software architecture The Motor Drive Control (MDC) The Position Readout and survey (PRS) Conclusions

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• The LHC collimation system • Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC • The PRS • Conclusions

Circumference: 26.7km Beam energy in collision: 7 TeV Dipole field at 7 TeV: 8.33 T Luminosity:1034 cm -2.s -1 Operating temperature: 1.9 K

A. Masi, R. Losito LHC Collimators low level control system

The LHC nominal beam energy is equivalent to:


One US aircraft carrier at 11 knots A mis-stereed beam can provoke: 1. Damage to the machine The energy in the two LHC beams is sufficient to melt almost 1 ton of copper

2. Quenches: For example, local transient loss of 4 × 107 protons at 7 TeV

The LHC collimation system has to protect a machine of 2 billions $ and reduce noise to the LHC experiments absorbing particles out of the nominal beam core See details at: http://lhc-collimation-project.web.cern.ch/lhc-collimation-project


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A collimator has two parallel jaws Each jaw is controllable in position and angle • The LHC collimation system • Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC

The jaws need to be positioned with 10 um accuracy

• The PRS • Conclusions


The collimation system is based on different collimators types and

• The LHC collimation system

up to 108 collimators distributed over 6 points in the machine

• Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC • The PRS • Conclusions

Jaw positions are correlated primary – secondary– tertiary Also during movements they have to stay in sync


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88 Collimators spread over 410 m • The LHC collimation system • Control requirements • Control system layout

30 Collimators spread over ~700 m

•The RT platform used • Control system software architecture • The MDC • The PRS • Conclusions

Control racks up to 700 m far from motors and sensors




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Reliability: since collimators protect the machine the first requirement of the control system is reliability

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Jaws positioning accuracy: fraction (1/10…) of the beam size (200µm!!).

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Syncronization between the two motors of the same jaw: much less than 1 ms to reduce vibrations

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Motion profiles: jaws in different collimators need to be locked for more than 20 minutes to movement functions sent by a central supervisory application. The motion start is provided by a Trigger sent via optical fiber

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Response delay to a Digital trigger: < 1ms

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Syncronization between all the 555 collimators motors all along a motion profile: < 10 ms



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Survey frequency: position sensors have to be read at least at 100 Hz to check in Real-Time that the actual position lies within a given limit function

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Synchronization between survey process and profile generation: lag time 200 us

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Low level rack dimensions: maximum 400mm deep. Limited space in the rack (in one 400 mm deep rack we need to install the controls for at least two

• The LHC collimation system • Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC

collimators)

• The PRS • Conclusions


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PXI systems by National Instruments have been used as RT platform because of: • The LHC collimation system • Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC • The PRS • Conclusions

• their robustness and compactness • the new RT controllers based on Intel Dual Core processors with solid state disk are powerful and reliable • the built -in 10 MHz signal architecture allows easy daisy chaining of a synchronization clock across multiple chassis through BNC connectors on the back of the chassis • 3 Mgate FPGA cards with analog I/O are available • A wide variety of cards is available and provided with LabView RT drivers. This allows saving manpower on the drivers’ deveolpment A. Masi, R. Losito LHC Collimators low level control system

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Clients

Java Control RAD programs C Programs The DIM Programs new (Distributed Front-End (VB, Excel) Information Software Architecture Management Middleware (FESA) Client is API a Device/Property Model Topic Model comprehensive System) is a communication framework forsystem designing, for distributed coding and/ mixed environments LynxOS/Linux based on the • The LHC collimation maintaining system equipment-software client/server paradigm that provides a stable functional • Control The DIM system is currently available requirements abstraction of accelerator for mixed platform environments devices • Control system comprising the operating systems : See details at: layout VMS, several Unix flavors (Linux, Solaris, HP-UX, Darwin, etc.) Windows http://project•The RT platform used NT/2000/XP and the real time OSs: fesa.web.cern.ch/project-fesa CMW Infrastructure CORBA, RDA, JMS

• Control system software architecture • The MDC • The PRS • Conclusions

OS9, LynxOs and VxWorks. It uses as network support TCP/IP (See details at http://dim.web.cern.ch/dim/ )

The DIM Server library was successfully compiled for Pharlap


Timing Card 6 6 5 3 with 45 ppb clock stability



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• The LHC collimation system • Control requirements • Control system layout •The RT platform used

Output updating:

• Control system software architecture

• Step and direction signals

• The MDC

• Analog outputs for resolvers excitation

• The PRS

Input readings:

• Conclusions

• Limit switches • Sin and cos signals from resolvers


Trigger delay

• The LHC collimation system • Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC

Start jitter Profile duration

Stop jitter

Trigger delay ~ 100 us

• The PRS

Start jitter: few us

• Conclusions

Stop jitter: 100 us Profile duration: ~20 minutes A. Masi, R. Losito LHC Collimators low level control system

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All the PXIs chassis are syncronized with the 10 MHz clock. A. Masi, R. Losito LHC Collimators low level control system



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LVDT working principle A ( x) − A2 ( x) r ( x) = 1 A1 ( x) + A2 ( x) • The LHC collimation system

The signal amplitude is estimated with a sine-fit algorithm

• Control requirements

(

~ x0 = DT0 D 0

• Control system layout

)

−1

D T0 y = D†0 y

A = Ac2 + As2

 y1  cos(2πf0t1) sin(2πf0t1) Ac     y cos(2πf0t2 ) sin(2πf0t2) 2   y =  , x0 = As , D0 =    M  M M O0     yN  cos(2πf0tN ) sin(2πf0tN )

•The RT platform used • Control system software architecture • The MDC • The PRS

1  1 . M  1

The algorithm is optimized for RT implementation

• Conclusions


21 LVDTs are read in less than 1 ms with a negligible jitter. The requirement about 100 Hz reading frequency is easily satisfied • The LHC collimation system • Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC • The PRS • Conclusions

Multiple reading characterization: the crosstalk has been rejected carefully choosing the excitations frequencies

Different SNR scenarios have been simulated adding noise on the LVDT secondaries. The accuracy will remain below few um


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• The LHC collimation system

Trigger delay

• Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC • The PRS • Conclusions

Start jitter Profile duration

Stop jitter

Trigger delay: 100 us reading jitter: 100 us Stop reading jitter: 200 us Survey profile duration: ~20 minutes A. Masi, R. Losito LHC Collimators low level control system



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• The LHC collimator low level system is reliable and robust: redundancy and fault tolerance have been built by separating the motor control and the position survey on different units • The LHC collimation system • Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC • The PRS • Conclusions

• PXI running LabView RT has been chosen as low level RT platform • Delay between trigger and motor movements is below 100 us • Position sensors can be read at frequencies close to 1 KHz • 120 chassis are synchronized using a 10 MHz clock • This configuration has been extensively tested in laboratory and in the CERN SPS confirming fulfillment of all the specs in a real (noisy) accelerator environment A. Masi, R. Losito LHC Collimators low level control system

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We Thank R. W. Assmann, M. Jonker, M Sobczak and S. Redaelli for the long discussions on the architecture of the collimation control system. Our colleagues of the AB/ATB/LPE section, in particular A. Brielmann, G. Conte, M. Donze, P. Gander, J. Lendaro and M. Martino for the fruitful collaboration on the implementation of the system. A. Masi, R. Losito LHC Collimators low level control system

• The LHC collimation system • Control requirements • Control system layout •The RT platform used • Control system software architecture • The MDC • The PRS

We are indebted to NI for the precious support received. In particular the System Engineering Group (Doug, Brent and Christian) and all the R&D people that were involved in this project as well as the European team (Stefano, Joel, Christian). Last but not least Chris and Giuseppe

• Conclusions


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• The LHC collimation system • Control requirements • Control system layout •The RT platform used

Thank you very much for your attention

• Control system software architecture • The MDC • The PRS • Conclusions


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