ATF Energy Spectrometer Experiments

Transcription

1 ATF Energy Spectrometer Experiments Mike Hildreth representing Energy Spectrometer Enthusiasts

2 ATF Basics 6 BPMs (3 per side) separated by 3?m LLNL (passive) girder KEK (active) girder Ultimate Goal: Measurement of two-platform relative stability at <50nm level KEK nano-bpm Optical Anchor LLNL/SLAC nano-bpm

3 Ingredients BPM resolution External position monitor read-back resolution Reproducible Calibration methods (internal systematics) Control of external systematics Stability of all components Stability Stability Stability All of the above can be achieved by design, once we understand what to design

4 BPM resolution BPMs: : Specific Suggestions The better (and more stable) the resolution, the easier the rest of the design problem must be understood as completely as possible, including all possible biases and systematic errors Continue analysis aimed at understanding resolution effects, waveform fitting, etc. etc. Continue development of calibration procedures gain calibration? exploit multi-bpm systems to bootstrap beam stability issues? Studies of resolution variation across triplets???? inner vs. outer vs. middle some of these you were going to do anyway...

5 Position Monitoring Optical Linkage connecting the two BPM stations with an optical reference of sufficient resolution is as important as the BPM resolution heartily encouraged! multiple techniques should be tried, if possible straightness may be all that is necessary less resolution needed in other plane(s)? Studies of short and long-term stability internal consistency of position resolutions variation of resolution across system? cross-calibrate with movers?

6 Calibrations BPMs continue development of calibration methods to look at relative gain calibration beam angles vs. known offsets from movers position calibration movers, beam offsets tilt calibration? Position Measurement cross calibration with movers absolute scale? need <50nm resolution over 1 cm! redundant systems?

7 External Systematics BPMs position dependence on beam current position dependence on beam tails, synchrotron radiation sensitivity to beam centering sensitivity to changing beam conditions shielding issues? Position Measurements Studies of resolution variation with environmental conditions effects of radiation? beam pickup? Trajectory Determination effects of stray magnetic fields earth s field

8 Stability Everything in the system needs to be measurable or stable over ~1 hour tracking drifts with sufficient resolution is fine better not to have them! Electronics Temperature Gains Calibrations Position monitoring resolution

9 Is a full Spectrometer Test worth it? At ATF, unless it comes for free, it s probably not worth the effort of putting in a chicane to do a real energy measurement this will be mocked-up at ESA better to use the pristine conditions at ATF to extract the utmost resolution and stability from the system systematic understanding is always easier if you have complete control over the environment, initial conditions the more performant the position resolution/stability, the easier it is to build the spectrometer

10 Conclusions ATF is probably the ideal place to push BPM resolution and stability studies to their limits crucial design parameters for the Energy Spectrometers