Transcript Folie 1

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
42nd Meeting of the COSY Programm Advisory Committee
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.
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Outline
Three recent achievements
Proposed experimental investigations:
1. Spin coherence time studies (contin. of #176)
2. RF E × B Wien Filter
3. Systematic study of machine imperfections using two
straight section solenoids
Beam request
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A 1: Spin coherence time
Sextupole corrections of higher order effects yield 𝝉𝑺𝑪 = 𝟒𝟎𝟎 𝐬
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A 2: Spin tune determination
Using time stamping technique from Up/Do asymmetry 𝑨 𝒕 ∝ 𝒆
−
𝒕
𝝉𝐒𝐂
∙ 𝐬𝐢𝐧 𝝎𝒕
Spin tune 𝝊𝒔 determined to ≈ 𝟏𝟎−𝟖 in 𝟐 𝐬.
Average 𝝊𝒔 in one cycle (≈ 𝟏𝟎𝟎 𝐬) known to 𝟏𝟎−𝟏𝟎 .
Understand implications for future precision experiments.
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A 3: Harmonic dependence of 𝝉𝐒𝐂
𝜏SC =
1
2𝜋 2 𝐶 2 𝑓rev 𝐺 2 𝛾 2 𝛽4
∆𝑝
𝑝
2 −1
Deuterons
Spin coherence time (s)
𝑓RF = 𝛾𝐺 ± 𝐾 𝑓rev
Spin coherence time (s)
Observed oscillating 𝑃𝑦 , driven by
RF solenoid at different harmonics 𝐾
1
8
1
10
1
10
1
10
K=1 (630 kHz)
K=-1 (871 kHz)
K=2 (1380 kHz)
K=2 (1620 kHz)
6
235 MeV
4
100
1
10
𝜂
𝐾
𝐶 =1− 2 1+
𝛽
𝛾𝐺
RF-B solenoid
10
10
Beam
100 energy (MeV)
1
3
10
1
4
10
Beam energy (MeV)
Theory: N.N.Nikolaev
Observation of enhancements
of 𝝉𝐒𝐂 for p (and d) requires
more flexible polarimeter
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1. Spin coherence time studies (contin. of #176)
Removing spin tune spread with sextupole fields:
• Observe result in lifetime (SCT) of horizontal polarization
• Major run in weeks 35 and 36 (August/September) 2013 (lots of data)
Example of data measured with the
time-marking DAQ system
Zero crossing of inverse
slope locates best SCT.
SCT
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Initial Polarization Slope
HORIZONTAL POLARIZATION
black = spin down
blue = spin up
signs changed to
show linear effect
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First 2-D Map: 𝝉𝐒𝐂 vs MXS vs MXG
Location of best SCT is closely associated with location of vanishing
chromaticity.
MXS
+
+ Best SCT points for
+
large horizontal emittance
40
+ +
large Δp/p (longitudinal)
+
• Each sextupole field scan
locates one point on 2D map
• Beam set up to emphasize
different sources of
decoherence, which can be
corrected with sextupole fields.
+ Best SCT points for
+ +
++
+
20
ξX = 0
+
+ +
ξY = 0
Units: percent of power
supply full scale.
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0
+
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+
20
MXG
8
Chromaticity studies (tests in week 7)
Chromaticity 𝜉 defines the tune change with respect to momentum deviation
𝚫𝑸
𝚫𝒑
=𝝃⋅
𝑸
𝒑
• Strong connection between 𝜉𝑥,𝑦 and 𝜏𝑆𝐶 observed.
• COSY Infinity based model predicts negative natural chromaticities 𝜉𝑥 and 𝜉𝑦 .
• Measured natural chromaticity: 𝜉𝑦 > 0 and 𝜉𝑥 < 0.
• 𝜉𝑦 changed from 1 to 3 in 2013, although similar machine settings were used.
To be studied:
• Vary sextupoles of arcs and straights: benchmark 𝝃 changes in model.
• Vary quadrupoles and orbit excitations to search for sources of 𝝃 variations.
• Examine long term stability.
• Ramp up dipole magnets to investigate influence of machine history on 𝝃 .
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Measurement of chromaticity
Two methods for beam energy shift applied
1. Variation of electron cooler voltage
2. Variation of cavity frequency
Tune measurement:
• Sweep frequency for beam excitation and
measure response to locate betratron frequency
• Measure revolution frequency using Schottky
spectrum
Horizontal
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Vertical
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Chromaticity: Arc sextupoles
Three families in the arcs: (MXS, MXL, MXG)
Non-vanishing dispersion in the arcs, large influence of chromaticity expected
Measurement / Model (change per %)
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MXS:
0.1486 / 0.1337
−0.1130 / −0.1046
MXL:
0.1555 / 0.1628
−0.7532 / −0.7484
MXG:
0.2146 / 0.2298
−0.1703 / −0.1626
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Chromaticity: Straight section sextupoles
Test of combined familiy of four straight section sextupoles (MXT: 2-3-10-13)
Dispersion minimized in straights, no impact on chromaticity expected
Straight section sextupoles show no effect on chromaticity
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Spin coherence time studies: Required time
2 weeks are requested to further explore ways to improve the SCT.
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.
2. Explore straight section sextupoles (no effect on chromaticity)
• Sensitivity of SCT seen before (but weaker). Does different degree of
freedom help?
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 to SCT in white noise extraction
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2. RF 𝐄 × 𝐁 Wien Filter
Precursor EDM concept: Use RF Wien filter to accumulate EDM signal
Insert RF-𝑬𝒙 dipole into ceramic
chamber
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RF 𝐄 × 𝐁 Wien Filter: Field calculations
Main field component
𝐸𝑦 = 7594 V/m at y = 0,
U = 395 V,
𝑬𝒚 𝒅𝒛 = 𝟒𝟖𝟏𝟖 𝐕
𝑩𝒙 (𝐓)
𝑬𝒚 (𝐕/𝐦)
𝑩𝒙 𝒅𝒛 = 𝟎. 𝟎𝟑𝟓 𝐓𝐦𝐦
𝒛 (𝐦)
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Integral compensation of Lorentz
force 𝐹𝑦 𝑑𝑧 = 0 at y = 0
𝑭𝒚 (𝐞𝐕/𝐦)
Main field component
𝐵𝑥 = 0.058 mT at 𝑦 = 0, 𝐼 = 1 A,
𝒛 (𝐦)
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𝒛 (𝐦)
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RF 𝐄 × 𝐁 Wien Filter: First tests with beam
Commissioning:
• Pulsed mode, 40 pulses, each 10 ms long,
• BPM sensitivity at betatron sideband frequency 𝑓𝛽𝑦 = 𝑓RF−E×B = 1186 kHz
used to adjust E and B to match Wien filter condition,
• Diagnosis using COSY BCT
Matching of phase of 𝐸, 𝐵 at 𝐼 =
0.27 A, 𝑈 = 121 V
Beam loss (%)
Beam loss (%)
Matching of RF 𝐵 field to RF 𝐸 at 𝑈 = 121 V
𝐼 (A)
E-B phase (°)
• Compensation achieved down to ~7 % beam loss.
Requested 2 weeks of beam time will be used to fully commission the RF
E × B Wien filter, should do same job as RF solenoid.
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Systematic study of machine imperfections
using two straight section solenoids
Systematic effects from machine imperfections limit the achievable
precision in a precuror experiment using an RF E × B Wien filter.
Idea: The precise determination of the spin tune
Δ𝜐𝑠
𝜐𝑠
≈ 10−10 in one cycle
can be exploited to map out the imperfections of COSY.
COSY provides two solenoids in opposite straight sections:
1. one of the compensation solenoids of the 70 kV cooler:
𝑩𝒛 𝒅𝒛 ≈ 𝟎. 𝟏𝟓 𝐓𝐦,
2. The main solenoid of the 2 MV cooler: 𝑩𝒛 𝒅𝒛 ≈ 𝟎. 𝟓𝟒 𝐓𝐦.
Both are available dynamically in the cycle, i.e., their strength can be
adjusted on flattop.
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Imperfection kick: Deuterons at 𝑻 = 𝟐𝟐𝟑 MeV
Ideal machine with vanishing static
imperfections: Saddle point at the origin
sea level at 𝐺𝛾 (= 0.16) − 5 ∙ 10−7
Intrinsic imperfection kick 𝛼𝑥 = 0.001
shifts saddle point away from origin
Location of imperfection: Θ∗ = 𝜋 3
The requested 2 weeks of beam time shall be used to study static imperfections
with artificial spin rotations 𝜒1 and 𝜒2 induced by two straight section solenoids.
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Beam Request
• We request in total 6 weeks of beam time for the activities:
1. Spin coherence time studies (contin. of #176) (2 weeks),
2. RF E × B Wien Filter
(2 weeks),
3. Systematic study of machine imperfections
using two straight section solenoids
(2 weeks),
preceeded by 1 MD week.
• Investigations difficult, require time consuming machine tuning.
Beam time should be scheduled as single block.
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Backup slides
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Precursor experiments: RF methods
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
Use existing magnetic machines for first direct EDM measurements
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Precursor experiments:
1. Resonance Method with „magic“ 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.
𝑬∗ = 𝟎  𝑬𝑹 = −𝑩𝒚
RF E(B)-field
stored d
„Magic RF Wien Filter“
In-plane
polarization
no Lorentz force
→ Indirect EDM effect
Observable:
Accumulation of vertical
polarization during spin
coherence time
Polarimeter (dp elastic)
Statistical sensitivity for 𝒅𝒅 in the range 𝟏𝟎−𝟐𝟑 to 𝟏𝟎−𝟐𝟒 𝐞𝐜𝐦 range possible.
• Alignment and field stability of ring magnets
• Imperfection of RF-E(B) flipper
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Precursor experiments:
1. Resonance Method for deuterons at COSY
Parameters:
𝑷𝒙
beam energy
assumed EDM
E-field
𝑇𝑑 = 50 MeV
𝑑𝑑 = 10−24 ecm
30 kV/cm
𝑷𝒛
𝐿RF = 1 m
𝑷𝒚
𝜔 = 2𝜋𝑓𝑟𝑒𝑣 𝐺𝛾
= −3.402 × 105 Hz
𝐭𝐮𝐫𝐧 𝐧𝐮𝐦𝐛𝐞𝐫
EDM effect accumulates in 𝑃𝑦
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1. Resonance Method
Operation of „magic“ RF Wien filter
𝑓𝐻𝑉
Radial E and vertical B fields oscillate, e.g., with
= 𝐾 + 𝐺𝛾 ∙ 𝑓rev = −54.151 × 103 Hz (here 𝐾 = 0).
beam energy
𝑇𝑑 = 50 MeV
Spin coherence time may depend on excitation and on harmonics 𝐾.
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Precursor experiments:
1. Resonance Method for deuterons at COSY
Parameters:
beam energy
assumed EDM
E-field
𝑇𝑑 = 50 MeV
𝑑𝑑 = 10−24 ecm
30 kV/cm
𝐿RF = 1 m
𝑃𝑦
𝑷𝒚
EDM effect accumulates in 𝑃𝑦
𝐭𝐮𝐫𝐧 𝐧𝐮𝐦𝐛𝐞𝐫
Linear extrapolation of 𝑷𝒚 for a time period of
𝑠𝑐 = 1000 s (= 3.7108 turns) yields a sizeable 𝑷𝒚 ~𝟏𝟎−𝟑 .
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Development: RF E/B-Flipper (RF Wien Filter)
1. Upgrade test flipper with electrostatic field plates ready end of year.
2. Build lower power version using a stripline system
3. Build high-power version of stripline system (𝑬 > 𝟏𝟎𝟎 𝐤𝐕/𝐦)
Work by S. Mey, R. Gebel (Jülich)
J. Slim, D. Hölscher (IHF RWTH Aachen)
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Precursor experiments:
2. Resonant EDM measurement with static Wien Filter
𝑷𝒙 (𝒕)
Machine operated on imperfection spin resonance at 𝜸𝑮 = 𝟐
without
static WF
Spin rotation in phase with orbit motion
𝒕 (𝐬)
Similar accumulation of EDM signal, systematics more difficult, strength of
imperfection resonance must be suppressed by closed-orbit corrections.
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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 “best case” chromaticity setup might work, as before.
2
ξX,Y = 0
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.
[email protected]
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Removing spin tune spread with sextupole fields
Observe result in lifetime (SCT) of horizontal polarization
Major run in weeks 35 and 36 (August/September) 2013, lots of data
HORIZONTAL POLARIZATION
MXS
Example of data
measured with the
time-marking
DAQ system
SCT
+
+
+ +
Best SCT
+
points for
+ +
Best SCT points
large Δp/p
+ + for large horizontal
(longitudinal)
emittance
20
Initial
Polarization
Slope
Zero crossing
of inverse slope
locates best SCT.
black = spin down
blue = spin up
[email protected]
40
Beam set up to
emphasize different
sources of decoherence,
which can be corrected
with sextupole fields.
Each sextupole
field scan locates
one point on
2-D map.
signs changed to
show linear effect
+
+
FIRST
2-D
MAP
+ +
MXG
+
Units are in
0
percent of power
Search for Permanent
Electric
Dipole Moments at COSY
supply
full scale.
+
20
29
Results comparable to calculated slopes
for best SCT (X, Y emittance, and
longitudinal Δp/p) and zero chromaticity.
Location of best SCT is closely
associated with location of
vanishing chromaticity.
MXS
+
+
Slopes scaled to
percent units.
Offsets are
arbitrary.
40
+ +
Best SCT
points for
large Δp/p
(longitudinal)
Best SCT points
for large horizontal
emittance
++
+
+ +
+
20
COSY-Infinity calculations
by Marcel Rosenthal
Chromaticity effects are planar.
Sextupoles adjust constant term.
ξX = 0
+
+ +
ξY = 0
Units are in percent
of power supply
full scale.
+
0
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+
20
MXG
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best fit to
chromaticity
data
30
Stability
 5 days/nights of measurement
MXS @ 2%
shift of +0.3 expected
MXS @ 2%
shift of -0.22
expected
Measurements using cavity (method 2)
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Machine History
 Super Cycle:
B-Field of
bending
dipoles
1. cycle: no injection, dipole ramped to larger target momenta for 4- 5 seconds
2. cycle: usual measurement cycle
Additíonal dipole ramp
measurement
time
Target momenta of additional ramp:
1: 2028 MeV/c
2: 2513 MeV/c
3: 3097 MeV/c
4: 3700 MeV/c
5: cycle 1 removed
(default target momentum: 970 MeV/c
restoring
restoring
increasing
decreasing
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Physics: Fundamental Particles
Charge symmetric
 No EDM (𝒅 = 𝟎)
: MDM
𝒅: EDM
Do particles (e.g., electron, nucleon) have an EDM?
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Physics: Symmetries
Physical laws are invariant under certain transformations
Parity:
𝑷:
𝒙
−𝒙
𝒚 → −𝒚
𝒛
−𝒛
T-Symmetry:
𝑻:
𝒕 → −𝒕
C-parity (or Charge parity):
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Changes sign of all quantized charges
• electrical charge,
• baryon number,
• lepton number,
• flavor charges,
• Isospin (3rd-component)
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EDMs: Discrete Symmetries
Not Charge
symmetric
𝒅 (aligned w/ spin)
Permanent EDMs violate P and T.
Assuming CPT to hold, CP violated also.
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Physics: Potential of EDMs
J.M. Pendlebury: „nEDM has killed more theories than any other single expt.“
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Principle: Frozen spin Method
   
For transverse electric and magnetic fields in a ring (   B    E  0 ),
anomalous spin precession is described by Thomas-BMT equation:
 
2



 m  E

q 
G   G  B  G    

m
p
c

  



x
g 2

G 

2 

Magic condition: Spin along momentum vector
1. For any sign of 𝐺, in a combined electric and magnetic machine
GBc 2
2
E

GBc

1  G 2 2
2.
𝐸 = 𝐸radial
𝐵 = 𝐵vertical
For 𝐺 > 0 (protons) in an all electric ring
2
m
m
G     0  p 
G
 p
 700 .74
MeV
c
(magic)
 Magic rings to measure EDMs of free charge particles
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Beat systematics: BNL Proposal
2 beams simultaneously rotating in an all electric ring (cw, ccw)
CW & CCW beams cancels systematic
effects
CW
CCW
Polarization (𝑷𝒛)
+
−
+
−
EDM (𝒅 × 𝑬)
−
+
+
−
Sokolov-Ternov
−
−
+
+
Gravitation
−
+
−
+
Status: Approved BNL-Proposal
Submitted to DOE
Interest FNAL!
Goal for protons
 d  2.5  1029 e  cm (one year)
p
Many technological challenges need to be met
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srEDM searches: Technogical challenges
Charged particle EDM searches require development of a new
class of high-precision machines with mainly electric fields for
bending and focussing.
Related topics:
• Electric field gradients (~ 17
MV
at ~2 cm)
m
• Spin coherence time (≥ 1000 s)
• Continuous polarimetry < 1 ppm
• Beam positioning 10 𝑛𝑚
• Spin tracking
These issues must be addressed experimentally at existing facilities
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Challenge: Electric field for magic rings
R𝐚𝐝𝐢𝐚𝐥 𝑬 field only

r2 2 80 m3 He 0 .05
r2 2 50 md  0 .48 Gd
Proton EDM
100
radius (m)
80
𝐸 = 17 MV/m
60
r1( E)
40
𝑟 = 24.665 m
20
0
5
10
15
20
25
30
35
E
E-field (MV/m)
Challenge to produce large electric field gradients
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Challenge: Niobium electrodes
DPP stainless steel
fine-grain Nb
Show one slide on JLAB data HV devices
large-grain
large-grain Nb
Nb
single-crystal Nb
Large-grain Nb at plate separation of a few cm yields ~20 MV/m
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Challenge: Electric field for magic rings
Electrostatic separators at Tevatron used to avoid unwanted 𝑝𝑝 interactions
- electrodes made from stainless steel
Routine operation at 1 spark/Year at 6 MV/m
~July 2013: Transfer of separator unit plus equipment from FNAL to Jülich
Need to develop new electrode materials and surface treatments
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Challenge: Spin coherence time
Spin closed orbit
one particle with
magnetic moment
makes one turn
nˆCO “spin closed orbit vector”
“spin tune”

S A

SA
ring
A
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2 s
stable
polarization

if S ║ nˆCO
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Challenge: Spin coherence time
We usually don‘t worry about coherence of spins along 𝑛𝑐𝑜
Polarization not affected!
At injection all
spin vectors aligned (coherent)
After some time, spin vectors get out of
phase and fully populate the cone
Situation very different, when you deal with 𝑆 ⊥ 𝑛𝑐𝑜 machines with frozen spin.
nˆCO
Longitudinal polarization
vanishes!
At injection all spin vectors aligned
Later, spin vectors are out of
phase in the horizontal plane
In an EDM machine with frozen spin, observation time is limited.
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44
Challenge: SCT stimates (N.N. Nikolaev)
One source of spin coherence are random variations of the spin tune
due to the momentum spread in the beam
𝛿𝜃 = 𝐺𝛿𝛾
𝛿𝛾
and
is randomized by e.g., electron cooling
cos 𝜔𝑡 → cos 𝜔𝑡 + 𝛿𝜃
𝑓rev 𝐺 2 𝛿𝛾 2
1
≈
𝑓rev 𝐺 2 𝛾 2 𝛽4
𝑇kin = 100 MeV
𝑓rev = 0.5 MHz
𝐺𝑝 = 1.79
𝐺𝑑 = −0.14
𝜏𝑠𝑐 (𝑝) ≈ 3 ∙ 103 s
𝜏𝑠𝑐 (𝑑) ≈ 5 ∙ 105 s
𝜏𝑠𝑐 ≈
Estimate:
1
𝛿𝑝
𝑝
2 −1
Spin coherence time for deuterons may be 𝟏𝟎𝟎× larger than for protons
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EDM at COSY: COoler SYnchrotron
Cooler and storage ring for (polarized) protons and deuterons
𝒑 = 𝟎. 𝟑 – 𝟑. 𝟕 𝑮𝒆𝑽/𝒄
Phase space
cooled internal &
extracted beams
COSY
Injector cyclotron
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…
…the
an spin-physics
ideal starting
machine
point
for
forahadron
srEDMphysics
search
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46
New Idea: Ivan Koop‘s spin wheel
𝑑𝑆
=𝑑×𝐸+𝜇×𝐵
𝑑𝑡
B
By appropriate choice of magnetic field, the spin vector
rotates fast → frequencies of the order kHz
Jülich has expertise in SQUIDs, state-of-the art
measurements allow for is 10−6 × Φ0
(Φ0 = 2.067833758 46 × 10−15 Wb)
This would revolutionize the way we conceive EDM (and in
general polarization) experiments, because frequencies
become directly measureable.
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How Ivan‘s spin wheel would work?
EDM ≠ 0
Frequency
EDM = 0
Find the value of B where
spin precession frequency
disappears
B field
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∼ Δ𝑦
48
SQUIDs: Precision tools for accelerators
Possible applications in accelerators, all of which are needed for
srEDM experiments
1. Beam current transformers
2. Beam position monitors
3. Beam polarimeters
Begin development with a measurement of
the noise spectrum using three coils:
• Coil 35mm away from center ANKE chamber
• Combined coils in same housing
• GHz range (one pickup loop)
• MHz range (several hundered loops)
• Fluxgate sensor
• kHz range
Measurement of noise spectrum at COSY in MD week, July 2013
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49
New Idea: Direct measurement of electron EDM
Bill Morse (BNL EDM): 𝑝 = 15 MeV/c, 𝑟~1.5 m, 𝛾~30
Nobody knows where CPV is hiding, may well be in the leptonic sector
Needs a dedicated R&D effort
Very attractive:
• Tests all ingredients of srEDM experiments with ≪ €
• Could develop into an independent long-term project
Polarimetry is an issue
Goal: < 10−27 e ∙ cm
Could be an option for FNAL using the electrostatic Tevatron separators
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50
Timeline:
Stepwise approach all-in-one machine for JEDI
Step Aim / Scientific goal
1
2
Device / Tool
Storage ring
Spin coherence time studies
Horizontal RF-B spin flipper
COSY
Systematic error studies
Vertical RF-B spin flipper
COSY
COSY upgrade
Orbit control, magnets, …
COSY
First direct EDM
measurement at 𝟏𝟎−𝟐𝟒 𝐞𝐜𝐦
RF-E(B) spin flipper
Modified
COSY
3
Built dedicated all-in-one ring Common magneticfor 𝑝, 𝑑, 3He
electrostatic deflectors
Dedicated
ring
4
EDM measurement of 𝑝, 𝑑,
3He at 𝟏𝟎−𝟐𝟗 𝐞𝐜𝐦
Dedicated
ring
Time scale:
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Steps 1 and 2: < 𝟓 years (i.e., in POF 3)
Steps 3 and 4: > 𝟓 years
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51
Georg Christoph Lichtenberg (1742-1799)
“Man muß etwas Neues machen, um etwas Neues zu sehen.”
“You have to make (create) something new,
if you want to see something new”
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