Instrumentation, Controls and MPS

M. Ross October 15, 2004

TRC R2:• The most critical beam instrumentation, including the intra-train luminosity

monitor, must be developed, and an acceptable laser-wire profile monitor must be provided where needed. A vigorous R&D program is mandatory for beam instrumentation in general; it would be appropriate for a collaborative effort between laboratories.

• Goals for this session:– instrumentation has limited leverage on the design as a whole– inexpensive in dollar terms but not in intellectual terms or testing time. – There needs to be interregional engineering teams to accelerate progress– Performance list of items and their relationship to present state of the art has

been made but needs serious engineering input – Understanding of the role of secondary specialized instrumentation also needed. Commentary on strategy for this RD Requirements / subsystem re-optimization

BPM Typical requirements• linac ~ 75 mm diameter

– TDR 10µm– USLCTOPS 1µm (provides much more LET headroom) [NLC

400nm @8mm]• to be revisited by 2004.12

– offset stability?• Beam delivery: much larger diameter, tighter

‘normalized’ resolution requirements• MDI (energy spectrometer)

– 100 nm stable for many minutes (needs prescription for operation)

• DR … both single pass and storage ring hardware needed– ATF 2µm single pass, 25mm

• near state of the art

Profile monitor – Typical requirements †

• micron dynamic range; few percent resolution– dynamic range: useful range of the device (minimal/correctable

systematic errors)– resolution: repeatability with given conditions – (how are the above validated?)– (typical SLC ~ 10% at full energy, 5% at DR exit – best

condition)– TESLA requirement (N. Walker): 2%– demonstrated at ATF ‘in the ring’: 1% @ 5µm. – world’s best

scanner– large aspect ratio problems coupling correction

• Calibration, Durability, Operability• beyond state of the art needed (?); testing and

development of tools important

• † not including beam delivery / IR

• Longitudinal:– this is where synergy with FEL’s will work best in our favor

– There is a ‘huge’ effort underway

• Correlation monitors– the next step in understanding emittance growth– projected phase space growth through correlation, e.g. y − z. – Transverse deflecting structures are being used to measure

‘slice emittance’• expensive and cumbersome to integrate

– Another beam correlation monitor is required.

Back to the source: existing machines

• performance (is/has been) limited by BPM resolution / offsets at SLC, LER, LEP and ATF– offsets, resolution and reliability

• In the last decade made excellent progress for 3rd generation light sources averaging and digital receiver techniques. General RD needed for LC. (FEL requirements not equivalent, more relaxed.)– single pass improvements – FFTB, ATF…– TTF relies more on screens

• Typical performance:– Storage ring multi-turn – offsets, resolution submicron– single pass (APS – scaled by chamber size to 75mm ILC) ~4um– single pass FFTB (scaled) ~ 3 um / small system

Instrumentation RD strategies

• to what degree does the ILC rely on instrumentation?– implementation of correction schemes in the TESLA design– TTF (until now) relied heavily on screens, less on BPM’s

• testing tolerance limits, understanding resolution ‘budget’– time for RD, time to prove trustworthy systems & reduce risk

• profile monitor performance verification /systematics studies– Controlled environment, dedicated test beams (ATF, ESA,

rings?)

MPS – What is it?• the set of all devices which

– allow continued smooth operation – provide minimal chance of beam-related component damage – prevent unacceptable levels of residual radioactivity.

• Integration of MPS means allocating redundancy to prevent simple single point faults

• Generally, – beamline components, – associated sensors, – beam diagnostic devices, – interconnection system – automated fault logging, – recovery sequence,– self-diagnosis used for prediction of beam loss at higher (than current)

power.

Machine Protection (MPS)• ranked highest risk by USLCTOPS• 2 most challenging problems – interconnected with beamline design

– single pulse damage• (what are the component by component consequences/results?) controversial for

BD– sequence control / integration– (average power loss protection will be a big, cumbersome system built to mimic

existing systems)• impact on component and beamline design (example)

– short loop ‘off-ramps’ within BD (looks like ‘FONT’ with fast BPM’s driving powerful kickers)

– Use benign leading pilot pulse spaced by a few interbunch gaps to clear system after the ~200ms hiatus (equivalent of MAID from warm)

– cold linac greatest problem is average power (like at TTF2 ~ 20KW at 5Hz/3MHz or 1Hz/10MHz)

• Session goals:– dissemination of interconnection issues– RD strategies (test beams, design criteria)

MPS Development Process ‘decision tree’:

• MPS development will require three stages (USTOPS): 1. understanding and testing the basic interaction between the

beam and beamline components, 2. development of mechanical engineering guidelines which result

in designs that are optimized from an MPS point of view and 3. development of controls strategies that are at once reliable,

redundant and flexible.

• Goals for this session:– Agree on the above notes– Commentary on (a) strategy for this RD– System ‘paradigm’ comments