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May 31, 2005Mike Hildreth – ATF 2005 Upstream Spectrometer Considerations “LEP-style” BPM-based Spectrometer –The only technique we could think of that gives required resolution while doing ~nothing to the beam very simple: Considerations: –Constrained by allowed emittance growth from SR –Constrained by available real estate in BDS, overall size These constraints determine needed BPM resolution/stability –Other issues drive systematic errors, diagnostics Complicated dependence on design parameters, options –Must be robust, invisible to luminosity Ancillary Magnet = 1.9 mrad 0m10m 2.5cm BPMs Spectrometer Magnet
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May 31, 2005 Mike Hildreth – ATF 2005
Energy Spectrometry and ATFEnergy Spectrometry and ATF
Components of the nano-BPM Test Program and Plans for Future Tests
Mike HildrethUniversity of Notre Dame
May 31, 2005 Mike Hildreth – ATF 2005
Spectrometry: A ReminderSpectrometry: A Reminder
• Required measurement precision is set by the expected statistical and systematic errors of “benchmark” measurements of mtop, mhiggs:
– require Ebeam/Ebeam ~ 100-200 ppm– (LEP2 achieved ~170 ppm with a combination of techniques)
Spectrometer Magnet
Ancillary Magnet
= 1.9 mrad
0m
10m
2.5cm
BPMs
“upstream”
“downstream”
BPM-based
WISRD-style
May 31, 2005 Mike Hildreth – ATF 2005
Upstream Spectrometer ConsiderationsUpstream Spectrometer Considerations
• “LEP-style” BPM-based Spectrometer– The only technique we could think of that gives required resolution
while doing ~nothing to the beam• very simple:
• Considerations:– Constrained by allowed emittance growth from SR– Constrained by available real estate in BDS, overall size
• These constraints determine needed BPM resolution/stability– Other issues drive systematic errors, diagnostics Complicated dependence on design parameters, options– Must be robust, invisible to luminosity
ec B dp Ancillary Magnet
= 1.9 mrad
0m 10m
2.5cm
BPMsSpectrometer Magnet
May 31, 2005 Mike Hildreth – ATF 2005
Design Decision DiagramDesign Decision Diagram
Required BPM Resolution
Chicane Length
Chicane Optics ()
d/ds from SRBend Radius
Bend Length(Bd)
Mechanical Stability
Beam angle jitter
Betatron jitter
(bunch charge)
Energy jitter
Major Design parameterExternal constraintExternal input
Ebunch or <E>?
May 31, 2005 Mike Hildreth – ATF 2005
PrototypePrototype
• Presented at January MDI Workshop at SLAC– first attempt at an optimization within the available parameter space– Assumes 1m BPM resolution– large, softer bends at high-dispersion point to minimize emittance growth
from synchrotron radiation– will need some iteration (from things learned on this trip!)
16.13
16.13
May 31, 2005 Mike Hildreth – ATF 2005
New BDS Optics (March)New BDS Optics (March)
new
May 31, 2005 Mike Hildreth – ATF 2005
Optics: detailsOptics: detailsenergy
collimation“tail-folding”
octupolesenergy spectrometer chicane
ΔX = 5 mm (on-energy)
May 31, 2005 Mike Hildreth – ATF 2005
Optics: more detailsOptics: more details
Δγεx = 1.2×10-10 @ 250 GeV= 7.5×10-9 @ 500 GeV
50m
small beam growth due to SR• high dispersion
– makes measurement easier• longer (~55m)
– ditto• Basically, meets many of the
constraints on spect design• (betatron phase issues while
scanning B field?)
Comments:
May 31, 2005 Mike Hildreth – ATF 2005
ATF: Excellent Test BeamATF: Excellent Test Beam
• Many tests directly relevant to spectrometer concepts– nano-BPM tests of ultimate resolution
• nice, small beams to work with– “optical anchor” under construction to connect two pairs of BPM triplets– optical straightness monitor with ~10nm resolution under development– resolution and stability tests
KEK nano-BPM LLNL/SLAC nano-BPMOptical Anchor
May 31, 2005 Mike Hildreth – ATF 2005
Nano-BPM testsNano-BPM tests
Overall Goal: <100nm Resolution Stability over ~hours– Factor of 10 better than current “strawman” design– if achievable, loosens many constraints, opens many options
• e.g., shorter chicane, smaller bends, bunch-by-bunch E, smaller pickup motion smaller pickup aperture, etc.
• Resolution:– ~20nm achieved(!)– With small ATF spots (~5-10m), but large jitter ( good test)– Can we get a 30-50m spot at the BINP pickups?
• Eventually, need to show desired resolution with “ILC” spot and betatron jitter (50-100m)
• if this can be done here easily, that would be a huge step
May 31, 2005 Mike Hildreth – ATF 2005
Nano-BPM testsNano-BPM tests
• Stability:– ~40nm achieved over 2 hours(!)
• In BINP pickups only– gain, phase calibration stable– (very impressive for a “first” try)
– Connection with KEK BPMs needed for full system test• Hopefully we can do this during the next three shifts• will give first look at how complicated a “real” system will be• understanding of resolutions, drifts will be critical
– both BPM systems need to be understood at the same level
May 31, 2005 Mike Hildreth – ATF 2005
Optical Monitoring TestsOptical Monitoring Tests
• Optical Anchor System:– more in later talks, but 6-D
measurements– Should give ~2 nm resolution in y
and z (=x), more like 40nm in x– will be very interesting to give
baseline numbers on absolute movements of components
– cross reference with Honda-san’s Straightness Monitor
stability, and more stability• how well do we need to do?• What optical system is
necessary?
KEK BPMSLAC BPM
Floor node
• position monitoring system is a critical component for Energy Spectrometry
• Planned installations will be the test bed for these systems
May 31, 2005 Mike Hildreth – ATF 2005
ConclusionsConclusions
• ATF + ATF2 will be important test beds for all aspects of Energy Spectrometry
– Test beam work necessary SOON to meet CDR time goal– Many parameters to consider– Emphasis is currently on hardware
• built-in redundancy will be key – in monitoring and measurement systems
– Truly international collaborations
• “Trust, but Verify”– Beam Tests are critical for these systems
• tolerances are very tight, many surprises are possible– Great Opportunities here to make progress
May 31, 2005 Mike Hildreth – ATF 2005
End Station A Test BeamsEnd Station A Test Beams
• T-474 (BPM Spectrometer) and T-475 (Wisrd Spectrometer) approved– will also incorporate collimator wake-field studies, other experiments
concrete shielding
Existing RF BPMs can be used for stability, resolution tests
Beamline components scavenged from SPEAR, other SLAC surplus
Nan
o-B
PM
s
Goal: Demonstrate Spect performance in “real beam”
May 31, 2005 Mike Hildreth – ATF 2005
ESA ProgramESA Program
• ESA provides “ILC-like” beam in “realistic” conditions:
– Can always tweak jitter parameters to make things worse– Can “simulate” beamstrahlung pair production by using radiators– Complementary to ATF tests