Recap on ELENA machine and challenges, … Topics studied recently (mostly work in progress)

Status of ELENA –Technical Report, Status of External Contributions

Christian Carli on behalf of the ELENA teams ADUC, 13th June 2012

Recap on ELENA machine and challenges, … Topics studied recently (mostly work in

progress) Lattice and acceptance Bending magnets with very low fields Electron cooling at low energy and equilibrium with

IBS Vacuum system and residual gas interactions Stray Field measurements

Status of external Contributions Summary

Recap on ELENA machine and challenges (Not that) short synchrotron decelerating p-bars

from the AD to very low energy of 100 keV Increase of phase space density by electron

cooling at (two) low energy Weak magnetic field (100 G planned at

present) to limit lattice perturbations Twiss parameter at cooler

D ≈ 1.4 m, bx≈ by ≈ 2 m Challenge for studies:

equilibrium beam parameters with IBSand other blow-up sources, cooler imperfections …

optimization of (lattice) parameters Electron beam potential creates parabolic electron

velocity profile (plotted for 0.5 and 1 mA at 100 keV)

Transfer lines Electrostatic lines proposed: cheap and

magnetic shielding simpler

H- (or other ion) source for commissioning13th June 2012 ELENA Status C.Carli on behalf of the ELENA team

Interaction length reduced to 0.8 m now

Recap on ELENA machine and challenges Direct space charge effects

Additional defocusing due toCoulomb repulsion

Non-linear, depending on positionin bunch

Tune shift and spread (rule of thumb:maximum -0.1 to -0.3 just an indication – true for low periodicity and energy?)

Limits intensity per bunch (or bunch length) Very low energy and, in consequence, low beam rigidity and

magnetic fields Deflection due to ~0.5 G earth magnetic field at 100 keV (beam rigidity

457 Gm): > 1 mrad/m Careful investigations on stray fields to be expected … good closed orbit

control Ratio between magnet gap and curvature radius not (that) small: correct

modeling of magnet entrance/exit

Good field quality of very low field magnets a challenge Instabilities

Possibly despite low intensity with small emittances (momentum spread) and energy

Large direct space charge impedance due to low energy

13th June 2012 ELENA Status C.Carli on behalf of the ELENA team

Anti-

Recap on ELENA machine and challenges Intra Beam Scattering (IBS)

Consider coordinate system movingwith (average velocity of) beam

Still unordered motion of beamparticles

Can be associated with temperature(beam cooling = reduction of thisunordered motion)

IBS: Coulomb scattering between beam particles

ELENA: longitudinal temperature (and relative velocities) small compared to longitudinal ones(longitudinal electron cooling faster than transverse one)

Likely to transfer heat from transverse plane to longitudinal plane Likely the main limitation for equilibrium emittances with electron cooling Several theories exist and give similar results taking into account:

“Dispersion” (describing how beam position depends on (relative) momentum offset) tends to generate horizontal emittance growth due to IBS

Variations of beta-functions (beam sizes) around ring, coupling between transverse planes…13th June 2012 ELENA Status C.Carli on behalf of the ELENA team

s(long. position)

x (t

rans

. pos

ition

)

Lattice and Layout Challenges (usual for low small rings) for lattice design and

optics Many constraints and few “free parameters” (quads)

Suitable working point and sufficient acceptances (small maximum beta function, but also large dynamic aperture with non-linearities)

Long straight with small dispersion for electron cooling .. Modeling of magnets with not that small gaps (compared to bending

radius) Many geometries and lattices studied since last autumn

Square, hexagonal,triangular shape, different quadrupole locations

Baseline lattice (QX≈2.3, QY≈1.3) chosen for further detailed studies

Discussion e.g. on acceptancesand apertures on-going


Pavel Beloshitsky

Lattice and Layout

Integration and mechanical design started (details later in Francois presentation)13th June 2012 ELENA Status C.Carli on behalf of the ELENA team

Francois Butin

and team

Bending magnets with very low fields

Magnets with very low fields(0.35 T to 0.05 T) required Non-linearities due to low

fields a possible issue Was this the limitation for low

energies in other machines? “Dilution”, i.e. mixing of

magnetic steel and non-magnetic (stainless steel laminations)

Higher field in magnetic laminations

Mitigation of non-linearities due to low fields

Many simulations carried out 2D and 3D, static and dynamic

effects, hysteresis effects … C-shape and H magnets …


Daniel Schörling

Inhomogeneity at low field: - Dominated by a gradient - Compensation with quad settings

DB/B 10-4

-10-4

0

~half the field at 100 keV

~1.5 the field at 100 keV

Bending magnets with very low fields

Bending magnet prototype (planned) to verify: Production process of a magnetic yoke

diluted with stainless steel plates. Field quality with chosen steel and

hysteresis Mechanical deformations Wish: test heating during bake-out (NEG

activation) Edge angle and end shim design.


Ratio Magnetic Steel: Stainless

Steel1:2

Magnetic: Non-

Magnetic

Minimum field 0.05 T

Maximum field 0.4 TMagnetic length

(straight) 1.0 mRamp rate 0.4 T/s

Good field region (square)

±30/cos(30°) mm

Local field quality ≤ ±2·10-4 1-B/Bref

Integrated field quality ≤ ±2·10-4 1-∫Bdl/

∫BrefdlTotal gap height 100 mm

Approximate pole width 330 mm

Edge angles 12 deg

Electron cooling at low energy and equilibrium with IBS

Code betacool Developed at JINR, Dubna Models electron cooling,

Intra Beam Scattering (IBS), RF system ….)

Cooling at 100 keV plateau Electron cooling current 0.5 mA Strong blow-up due to IBS limits

final momentum spread Energy spreads expected at experiments

increased by one order of magnitude!!(see presentation by Pavel)

Cooling times around 1 s Final physical rms emittances of

≈0.25 mm and ≈0.17 mm !


A. Smirnov (JINR), P.Beloshitsky,G.Tranquille, M.Martini

RMS emittances and rel. momentum spread

Capture after electron cooling RF capture after switching off

cooler Sufficiently slowly to avoid

non-adiabaticities Sufficiently fast to avoid

(longitudinal)blow-up due to IBS

Four bunches with 0.6 107 pbars each

Characteristics for experiments(with VRF,h=4 ≈ 500 V) Rms bunch length: ≈0.25 m Rms energy spread: ≈0.5 keV

(impact on experiments & design of lines!)


A.Smirnov (JINR), S.Hancock,

P.Beloshitsky, G.Tranquille, M.Martini

RMS emittances and rel. momentum spread

0 0.01 0.02 0.03 0.04 0.05 0.060.01

0.11

10100

1000

reference time, sec

RF

Vol

tage

, V

Required RF voltageunder discussion

(could be less than 500 V)

Vacuum system and rest gas interactions

Very first simulations of pressures around the ring Only H2 desorption with 1.203 10-12 Torr l s-1 cm-2 (realistic for baked

machine everywhere) Some pressure variations since H2 not pumped efficiently by NEGs

(assumed in the whole ring) Next (more realistic simulations for gas compositions and more realistic

hardware): Realistic gas loads for

heavier molecules Injection/ejection

equipments Transfer lines

(differential pumpingclose to ring)

Electron cooler Final apertures

(smaller aperturesreduce conductance)


10-1

2 Tor

r2.

53.

5

Position along a sector between bends

R.Kersevan

Vacuum system and rest gas interactions

Very low pressure and velocity at 100 keV Most p-bars do not interact with rest gas

molecules (black): in average ~40 s between interactions!

Nuclear interactions (red): very rare Large angle scattering outside acceptance

(orange): large cross section due to low energy (losses slow due to low pressure and velocity)

Small angle scattering (blue): several deflections of one p-bar at 100

keV very unlikely Rms angles (and blow-up) strongly

overestimated if p-bars undergoing large angle scattering angles are taken into account


NucleusElectrons

Stray field measurements in the AD hall

Motivation: Beam at very low energy in not that short machine sensitive to stray field Make sure that stray fields in the hall are not too strong

First - preliminary for the moment - selected results Earth magnetic field dominates at the position of future ELENA ring (few

locations with higher and lower fields understood and not an issue) …. Excellent news for ELENA ring

Stronger fields a few meters from an experimental solenoid (AEGIS) .. Watch out for lines


General field levelBVERTICAL ≈ 35 mT

BHORIZONTAL ≈ 30 mT

Scaffolding structure behind kicker spools:

150 mT (70 mT @ 0.2 m)

Field at AD ring concrete shielding blocks:|B|≈ 10 mT

No gross time dependence observed

M. Buzio

Beam Transfers and Lines

Studies on beam transfers (injection/ejection, lines) underway (see presentation tomorrow by W.Bartmann and G.Vanbavinckhove) Extraction channels Geometry of lines Optics Design Test triplet (by and at

ASACUSA)

13th June 2012 ELENA Status C.Carli on behalf of the ELENA teamASACUSA triplet (Courtesy: D.Barna, M.Hori and T.Koichi)

W. Bartmann, G.Vanbavinckhove many contributions from ASACUSA

Status of external Contributions


Univ. Tokyo and MPQ-MPI: - 2 MCHF (possibly electron cooler) - 7 FTE (identified, electrostatic transfer lines and devices) Cockcroft Institute & Univ’s and Swansea University: - Costing of the order of 500 kGBP has been applied by U Liverpool, - A proposal has been submitted for work : this would cover 2 Postdocs, some PhD students

and equipment; the overall funding requested is about 1 M€; a decision is expected until June. Denmark: - Applied for the money for bends and quadrupoles (Danfysik), possibly funding for a postdoc IKP-FZ Julich: - Several aspects of the source have been discussed in meeting on 27th of March in Juelich - Work has started and will be again discussed tomorrow afternoon: substantial development

work is required to make such a source operational for ELENA commissioning. Many interfaces to be clarified (vacuum with differential pumping, design of lines, integration, infrastructure …).

Univ. Brescia: 50 kEuros (to be transferred after ADUC) RIKEN (new since last ADUC)

- Compensation solenoids for electron cooler- Manpower (student)

TRIUMF: Help for design of electrostatic transfer lines Hemholtz Institute Mainz: Construction of supports Manne-Siegmann: Help with ELENA commissioning Berkeley: DOE does not (yet) support – MoU not signed, but discussion not yet abandoned! CEA-IRFU Saclay-SIGMAPHI: only prototypes are interesting for them – did not sign MoU, but

still discussions

Summary/Status Studies on-going on several technical issues

Better understanding of limitations at low energy Intra Beam Scattering (IBS) seems the dominant limitation for

ELENA Expect larger energy spreads at the experiments

Still many studies work in progress …. and some studies to be started (e.g. instabilities, IBS on ramps ….)

Status Aim: Technical Design Report (TDR) to be ready in autumn For other milestones and more details on some topics

(parameter, new building, experimental zones …) see presentations by Stephan, Pavel, François and Wolfgang

Memory of Understanding of collaboration signed this morning On track for first ELENA physics at the beginning of 2017

Thanks To everybody who helped with the preparation of this presentation For your attention13th June 2012 ELENA Status C.Carli on behalf of the ELENA team

Recap on ELENA machine and challenges, … Topics studied recently (mostly work in progress)

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