Mitglied der Helmholtz- Gemeinschaft Search for Permanent Electric Dipole Moments at COSY Step 1: Spin coherence and systematic error studies (Proposal 216.1) February 24, 2014 Frank Rathmann on behalf of JEDI 42 nd Meeting of the COSY Programm Advisory Committee
52
Embed
February 24, 2014 Frank Rathmann on behalf of JEDI
Search for Permanent Electric Dipole Moments at COSY Step 1: Spin coherence and systematic error studies (Proposal 216.1). February 24, 2014 Frank Rathmann on behalf of JEDI 42 nd Meeting of the COSY Programm Advisory Committee . Introduction. - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Mitg
lied
der H
elm
holtz
-Gem
eins
chaf
t
Search for Permanent Electric Dipole Moments at COSYStep 1: Spin coherence and systematic error studies
(Proposal 216.1)
February 24, 2014 Frank Rathmann on behalf of JEDI42nd Meeting of the COSY Programm Advisory Committee
Search for Permanent Electric Dipole Moments at COSY 2
Introduction
Present proposal merges activities from #176 and #216 under the flag of JEDI.
Aim: Use expertise of both groups to develop instrumentation and techniques for EDM searches at storage rings.
Chromaticity defines the tune change with respect to momentum deviation
โข Strong connection between and observed.โข COSY Infinity based model predicts negative natural chromaticities and .โข Measured natural chromaticity: and โข changed from 1 to 3 in 2013, although similar machine settings were used.
To be studied:โข Vary sextupoles of arcs and straights: benchmark changes in model.โข Vary quadrupoles and orbit excitations to search for sources of variations.โข Examine long term stability.โข Ramp up dipole magnets to investigate influence of machine history on .
Measurement of chromaticityTwo methods for beam energy shift applied1. Variation of electron cooler voltage2. Variation of cavity frequency
Tune measurement:โข Sweep frequency for beam excitation and
measure response to locate betratron frequencyโข Measure revolution frequency using Schottky
spectrum
Horizontal Vertical
[email protected] Search for Permanent Electric Dipole Moments at COSY 10
Search for Permanent Electric Dipole Moments at COSY 11
Chromaticity: Arc sextupoles Three families in the arcs: (MXS, MXL, MXG)Non-vanishing dispersion in the arcs, large influence of chromaticity expected
Precursor EDM concept: Use RF Wien filter to accumulate EDM signal
Insert RF-dipole into ceramic chamber
Search for Permanent Electric Dipole Moments at COSY [email protected]
RF Wien Filter: Field calculations
๐ (๐ฆ)
๐ (๐ฆ)
๐ฉ๐(๐)
Main field componentat ,
Main field componentat ,
๐ (๐ฆ)
๐(๐ฆ
)
๐ฌ๐(
๐/๐ฆ
)
๐ (๐ฆ)
๐(๐ฆ
)
๐ญ๐(๐๐/
๐ฆ)
Integral compensation of Lorentz force at
Search for Permanent Electric Dipole Moments at COSY [email protected]
RF Wien Filter: First tests with beamCommissioning:โข Pulsed mode, pulses, each long, โข BPM sensitivity at betatron sideband frequency used to adjust and to
match Wien filter condition,โข Diagnosis using COSY BCT
โข Compensation achieved down to ~7 % beam loss.๐ผ ( A)
Bea
m lo
ss (%
)
Matching of phase of at
Bea
m lo
ss (%
)E-B phase ()
Requested 2 weeks of beam time will be used to fully commission the RF Wien filter, should do same job as RF solenoid.
Matching of RF field to RF at
Search for Permanent Electric Dipole Moments at COSY 17
Systematic study of machine imperfections using two straight section solenoids
Idea: The precise determination of the spin tune can be exploited to map out the imperfections of COSY.
The requested 2 weeks of beam time shall be used to study static imperfections with artificial spin rotations and induced by two straight section solenoids.
Ideal machine with vanishing static imperfections: Saddle point at the origin
sea level at
Intrinsic imperfection kick shifts saddle point away from origin
Location of imperfection:
Search for Permanent Electric Dipole Moments at COSY 19
Beam Request
โข We request in total 6 weeks of beam time for the activities:1. Spin coherence time studies (contin. of #176) (2 weeks),2. RF Wien Filter (2 weeks),3. Systematic study of machine imperfections
using two straight section solenoids (2 weeks),preceeded by 1 MD week.
โข Investigations difficult, require time consuming machine tuning. Beam time should be scheduled as single block.
[email protected] Search for Permanent Electric Dipole Moments at COSY
Precursor experiments: RF methods
Use existing magnetic machines for first direct EDM measurements
Method based on making spin precession in machine resonant with orbit motion
Two ways: 1. Use an RF device that operates on some harmonics of the spin
precession frequency
2. Operate ring on an imperfection resonance
[email protected] Search for Permanent Electric Dipole Moments at COSY 22
Precursor experiments: 1. Resonance Method with โmagicโ RF Wien filter
Avoids coherent betatron oscillations of beam. Radial RF-E and vertical RF-B fields to observe spin rotation due to EDM.Approach pursued for a first direct measurement at COSY.
โMagic RF Wien Filterโ no Lorentz force Indirect EDM effect
Observable:Accumulation of vertical polarization during spin coherence time
Polarimeter (dp elastic)
stored d
RF E(B)-field In-plane polarization
Statistical sensitivity for in the range to range possible.โข Alignment and field stability of ring magnetsโข Imperfection of RF-E(B) flipper
[email protected] Search for Permanent Electric Dipole Moments at COSY 23
Precursor experiments: 1. Resonance Method for deuterons at COSY Parameters: beam energy
assumed EDME-field
๐ญ๐ฎ๐ซ๐ง๐ง๐ฎ๐ฆ๐๐๐ซ
๐ท ๐ ๐ท ๐ ๐ท ๐
EDM effect accumulates in
1. Resonance Method Operation of โmagicโ RF Wien filter
[email protected] Search for Permanent Electric Dipole Moments at COSY 24
Radial E and vertical B fields oscillate, e.g., with (here ).
beam energy
Spin coherence time may depend on excitation and on harmonics .๐พ
[email protected] Search for Permanent Electric Dipole Moments at COSY 25
Parameters: beam energy assumed EDME-field
EDM effect accumulates in
๐ ๐ฆ
๐ญ๐ฎ๐ซ๐ง๐ง๐ฎ๐ฆ๐๐๐ซ
๐ท ๐
Precursor experiments:1. Resonance Method for deuterons at COSY
Linear extrapolation of for a time period of yields a sizeable .
Search for Permanent Electric Dipole Moments at COSY 26
1. Upgrade test flipper with electrostatic field plates ready end of year.2. Build lower power version using a stripline system3. Build high-power version of stripline system ( )
Work by S. Mey, R. Gebel (Jรผlich)J. Slim, D. Hรถlscher (IHF RWTH Aachen)
[email protected] Search for Permanent Electric Dipole Moments at COSY
Precursor experiments:2. Resonant EDM measurement with static Wien Filter
Machine operated on imperfection spin resonance at
๐ท๐(๐
)
๐ (๐ฌ)Similar accumulation of EDM signal, systematics more difficult, strength of imperfection resonance must be suppressed by closed-orbit corrections.
Spin rotation in phase with orbit motion
without static WF
Search for Permanent Electric Dipole Moments at COSY 28
1 Make the lines of zero chromaticity coincide.Recent machine development studies provide the slopes for chromaticity vs. MXL (not tried before).A negative MXL setting should pull the zero chromaticity lines toward each other.A โbest caseโ chromaticity setup might work, as before.
ฮพX,Y = 0
2 Explore straight section sextupoles (no effect on chromaticity)Sensitivity of SCT seen before (but weaker).Does different degree of freedom help?
Based on analysis now underway, additional information would be useful:
3 Revisit RF-solenoid-induced PY oscillations at low field.Present analysis hampered by differential extraction on ridge target.
4 Explore contribution of emittance in white noise extraction to SCT.
Search for Permanent Electric Dipole Moments at COSY 29
Removing spin tune spread with sextupole fieldsObserve result in lifetime (SCT) of horizontal polarizationMajor run in weeks 35 and 36 (August/September) 2013, lots of data
MXG
MXS
0 20
20
40+
+
+
+
+
+
+
+
+
+
Best SCT points for large horizontal emittance
Best SCTpoints forlarge ฮp/p(longitudinal)
+
+
+
+
+
Units are inpercent of power supply full scale.
Example of datameasured with the
time-markingDAQ system
HORIZONTAL POLARIZATION
signs changed toshow linear effectblack = spin down
blue = spin up
Beam set up toemphasize different
sources of decoherence,which can be correctedwith sextupole fields.