Instrumentation, Controls and MPS

1. Instrumentation, Controls and MPS M. Ross October 15, 2004TRC 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

2. 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

3. 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

4. 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.

5. 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

6. 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?)

7. 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.

8. 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)

9. MPS Development Process ‘decision tree’: • MPS development will require three stages (USTOPS): • understanding and testing the basic interaction between the beam and beamline components, • development of mechanical engineering guidelines which result in designs that are optimized from an MPS point of view and • 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