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