1. A cold neutron beam facility for particle physics at the ESS
Torsten Soldner
Institut Laue Langevin
ANNI Proposers:
H. Abele, TU Wien
G. Konrad, TU Wien & SMI Wien
B. Märkisch, TU München
U. Schmidt, Uni Heidelberg
T. Soldner, ILL Grenoble
C. Theroine, ESS Lund
Aerial view ESS construction site
September 2016

2. Cold beam facility for particle physics at ESS
Advantages of the a
Long pulse source  high flux
Low repetition rate (14 Hz)  later frame overlap
First pulsed source with same time-averaged flux as the ILL(or even higher with final moderator design)
 We want a beamline there!
SPP 1491 – Nov 2015
Cold beam facility for particle physics at ESS

3. Statistics or Systematics??
Count rate: 400/s
Perkeo II
Fight against beam-related background
PSI2016
Cold beam facility for particle physics at ESS

4. Statistics or Systematics??
Count rate: 400/s
Perkeo II
40000/s
Perkeo III
Beam-related background!
Spectrometer response?
PSI2016
Cold beam facility for particle physics at ESS

5. Statistics or Systematics??
Statistics or Systematics??
Statistics and Systematics!
Count rate: 400/s
Perkeo II
40000/s
Perkeo III
400/s
Perkeo III pulsed
4000/s
Perkeo III pulsed at ANNI
See C. Roick
(poster) No
beam-related background
Well-defined spectrometer response
PSI2016
Cold beam facility for particle physics at ESS

6. Pulsed beams: Statistics and Systematics!
Spatial localization of neutron pulse
Separation of beam-related background
Separation of undefined spectrometer response
Time localization of neutron pulse
Signal/background
Suppression of background and drifts with different time constant
Separation by neutron wavelength
Velocity dependence of signal and systematics
Loss-free monochromatization
Time-dependent neutron optics
Wavelength-specific optics adapts to all neutrons
See F. Piegsa
(next talk)
PSI2016
Cold beam facility for particle physics at ESS

7. Science case Neutron beta decay with 10-4 accuracy
Broad-band probe for physics beyond the standard model, at scales of TeV
LoI by K. Bodek: Neutron decay correlations with BRAND
Absolute measurements in hadronic weak interaction
Systematic experimental study of QCD in non-perturbative regime
LoI by C. Crawford: Weak interactions between nucleons
New approaches to electromagnetic properties of the neutron
Beam methods for EDM and charge as probe for matter creation and unification of forces
LoI by F. Piegsa: Neutron EDM by beam method
Project open for you! More science very welcome!
For details, see this conference
PSI2016
Cold beam facility for particle physics at ESS

8. Design considerations
Maximum statistics at minimum systematics for versatile user instrumentation
Fully exploit pulse structure
Include polarization
Assure low background
Include ep/n separator
Optimize for beam quality
Provide flexibility
PSI2016
Cold beam facility for particle physics at ESS

9. Length of instrument  Short instrument: Maximum statistics
No frame overlap for high-intensity part of spectrum
Limit dilution of neutron pulse
Fully exploit pulse structure
 Short instrument:
14 Hz ESS, 8 Å  maximum length 34 m
(maximum ≡ neutrons leave experiment!)
Low background from source
Good wavelength resolution
Space to neighbors
PSI2016
Cold beam facility for particle physics at ESS

10. Cold beam facility for particle physics at ESS
ANNI – Overview
Moderator
Guide
Beam preparation
Experimental area
Extension
area
34 m
12 m
20 m
PSI2016
Cold beam facility for particle physics at ESS

11. Guide Concept Short guide 2 × out of sight Strong curvature Benders
20 m
2 × out of sight
Strong curvature
Benders
20 m
S-shape in vertical plane, because of moderator and polarization
Details optimized by McStas simulations for reference experiments
Element
Dist
[m]
Radius
Length
Cross-section
[mm2] #
m value γ*
[mrad] λ*
[Å]
Trumpet
2.0 ∞
3.6
88×60117×60 1
3.5 / 3.0
Straight 1
5.6
0.9
117×60
3.0
Bender 1
6.5
270
8.0 2
3.0, B: 3.5
14.7
2.44
Straight 2
14.5
0.4
Bender 2 / Polarizer
14.9
–84
2.5 6
3.0, T: 3.5
Anti-trumpet
17.4
4.6
117×60112×70

12. Cold beam facility for particle physics at ESS
Polarization options
Moderate polarization (98%) at highest intensity Bender 2 replaced by Polarizing bender
Highest polarization (>99.9%) Polarizing bender + bender in beam preparation area in X-SM geometry
Polarization with analytic wavelength dependence 3He spin filter in beam preparation area
X-SM bender
or 3He cell
Polarizing
bender
PSI2016
Cold beam facility for particle physics at ESS

13. Versatile chopper system
Highest intensity without frame overlap
Localization in Time or in Space
Monochromatization
Pulse multiplication
Dist
[m]
Radius
[cm]
Frequency
[Hz]
Angle
[º]
Comment
PDC1
6.5 40
14—70
Variable
2 co-rotating disks
FOC1 14 64
Single disk
FOC2
8.5 79
PDC2 26
PSC 60
PMC
Different slits
2 counter-rotating disks, replacing the disks of the PDC2
PSI2016
Cold beam facility for particle physics at ESS

14. Cold beam facility for particle physics at ESS
Chopper modes
Full intensity: Choppers off
Maximum intensity without frame overlap: Only FOCs
Time localization: PDC2 large opening + FOCs
Monochromatic: PDCs small 70 Hz + PSC + FOCs
Spatial localization: PDCs small 70 Hz + PSC + FOCs or pulse multiplication + FOCs
Frame overlap
suppression
until130 Å
Resolution at 8.9 Å:
0.55 Å FWHM
PSI2016
Cold beam facility for particle physics at ESS

15. Example: Pulse multiplication with PERC
Example: Pulse multiplication with PERC
fmax 70 Hz > 14 Hz of ESS
PMC
PSI2016
Cold beam facility for particle physics at ESS

16. ep/n separator as integral option
Available to all users
Fully optimized for ESS
Two detectors for improved systematics (stability monitoring, backscattering)
Profits from experience with PERC
Wien filter for protons
Electron detector
Electrostatic chopper & p detector
Magnetic spectrometer
MAC-E filter
R×B spectrometer
See aSPECT (talk & posters)
See G. Konrad (poster)
User
monitor
User
instrument B

17. Cold beam facility for particle physics at ESS
Performance
Parameter
Value
Capture flux full spectrum
5.4·1010 n/(cm2s) at guide exit
1.8·1010 n/(cm2s) at start of experimental area
Capture flux 2—8 Å (FOCs)
4.0·1010 n/(cm2s) at guide exit
1.4·1010 n/(cm2s) at start of experimental area
Particle 8.9 Å
5.8·108 / (cm2sÅ) at start of experimental area (with additional guide in beam definition area)
Divergence distribution FWHM
42 mrad horizontal
22 mrad vertical
Instantaneous bandwidth
0.43 Å
PSI2016
Cold beam facility for particle physics at ESS

18. Gain Signal / Background World leading from 1 MW ESS power
Benchmarks
Experiment
Facility
Gain Event rate
Gain Signal / Background
Comment
NPDGamma
FnPB (SNS) 15 1
Wavelength information
PERC
MEPHISTO (FRM II) 17 34
Pulse localization in spaceA
With PMCA
PERKEO III
PF1B (ILL) 6 16
Pulse localization in space
With PMC
aSPECT
0.4 3 10
Pulse localization in time at ANNI only
BeamEDM 25
Wavelength information, time dependent optical elements
World leading from 1 MW ESS power
PSI2016
Cold beam facility for particle physics at ESS

19. Cold beam facility for particle physics at ESS
Status and Outlook
Not hopeless. See info session this evening
PSI2016
Cold beam facility for particle physics at ESS

20. Cold beam facility for particle physics at ESS
Summary
Pulsed beams extremely useful for particle physics
Separation by wavelength
Time and spatial localization of pulse
Cleaner systematics
ESS has ideal time structure & brightness
Full beamline design and simulated performances:
ANNI will outperform all existing cold beam lines for particle physics, by 1-2 orders of magnitude
Need joint effort from community for realization ↖   
PSI2016
Cold beam facility for particle physics at ESS