Design Parameters of the new AD Electron Cooler...Courtesy of Didier Steyaert & Yannick Coutron Cooler more accessible. No need for working at heights. 5 x 5cm coils 2cm gap 12 x 1cm

Design Parameters of the new AD Electron Cooler

Lars Joergensen, Gerard Tranquille

Why a new electron cooler?

Present cooler is more than 40 years oldMissing spares – gun, collector solenoids & toroidAny intervention is time consuming and requires a lot of resources

Build a new state-of-the-art electron cooler incorporating the latest ideas for :• enhancing the cooling performance,• improving the vacuum in the cooling section,• easier intervention on the cooler,

and above all address the spares situation.

Maximum energy: 80 keV

Electron beam energy: 68.125 keV

Antiproton beam momentum: 500 MeV/c

Accelerating voltage: 68.808 kV

Relativistic beta: 0.471

Maximum electron current: 3.5 A

Cathode radius: 1.25 cm

Magnetic field in gun: 2400 G

Magnetic field in drift: 600 G

Expansion factor: 2

Beam radius in drift: 2.5 cm

Ne 7.9 x 1013 m-3

Drift solenoid length: 1.5 m

Cooler orientation: horizontal

Vacuum chamber diameter: 140 mm

Parameters

300 MeV/c 100 MeV/c

Electron energy / keV 26.2 3.05

Electron Current / A 2.5 0.1

Electron density / m-3 8.7 × 1013 1.0 × 1013

Energy dumped at coll. / kW 65.5 0.3

Magnetic field / Gauss 590

Electron beam diam. / mm 50 50

Cooling time / s 16 15

Cooling length / m 1.5

ex, ey / p mm mrad 1.6 / 2.4 <1 / <1

Dp/p ~2 × 10-3 <1 × 10-3

Cooling at a higher antiproton momentum (≤500 MeV/c)

Horizontal orientation

Electrostatic plates in each toroid.

NEG coated vacuum chambers.

Fast ramping of the expansion solenoid to adapt the electron beam size during cooling.

New solenoid design using pancakes and iron bars for the return-flux.

Compact orbit correctors (as used on ELENA).

What will be different?

During the AD deceleration the main losses occur at 300 MeV/c• x6.6 adiabatic blow-up between FT2 and FT3• Electron cooling performance relies on good stochastic cooling on FT2• Larger emittances on FT3 = longer cooling times, tail formation, more

critical alignment

By cooling at 500 MeV/c the blow-up is only a factor 4Shorter deceleration time:

• Better control of the tune and closed orbit• Avoid extra emittance blow-up due to resonance crossing

Transverse field in AD ecoolerDrift solenoid is ~ 3 x 10- 3

Horizontal orientation (proposal)Vertical orientation (present situation)

Cooler more accessible. No need for working at heights. Courtesy of Didier Steyaert & Yannick Coutron

5 x 5cm coils2cm gap12 x 1cm iron rods for the return flux

33cm coil1cm iron shield

New solenoid design (pancake structure)

• Fine adjustment of magnetic fieldpossible

• Only a handful of spare coils will beneeded

• Easier mounting• Lighter structure

Transverse Magnetic Field Measurements in the LEIR Cooler(compass)

200 250 300 350

x [cm]

0

-0.08

-0.16

-0.24

-0.32

-0.4

-0.48

Bx [G

au

ss]

200 250 300 350

x [cm]

0

0.4

0.8

1.2

-0.4

-0.8

By [G

au

ss]

200 250 300 350

0

0.0002

0.0004

0.0006

-0.0002

-0.0004B

xB

z

By

Bx

By/Bz for 750 Gauss

Beam expansion

• Needed for:

• Adapting the electron beam size to the injected beam size for optimum cooling.

– Reducing the magnetic field in the toroids, thus reducing the closed orbit distortion.

– Reducing the transverse thermal temperature of the electron beam.

Bo=0.24T, B=0.06T, ro=12.5mm => r=25mm

Bo=0.24T, B=0.06T, Eo=100meV => E=25meV

B

BrrconstrB oo2

//

o

o

t

B

BEEconst

B

E

//

Perveance = 2.93 A/V1.5

(anode:11.2 kV) Perveance = 1.38E6 A/V1.5

(anode:18.6 kV)

Perveance = 2.613E6 A/V1.5

(anode:12.15 kV)

New electron gun design (courtesy of Alexander Pikin)

0.0

2.0

4.0

6.0

8.0

10.0

12.0

2.0 2.2 2.4 2.6 2.8 3.0

Max

imu

m t

ran

sver

se e

ner

y, e

V

M field, kGs

Dependence of maximum transverse electron energy on uniform magnetic field for electron guns 25 mm diameter cathode with

different curvature radii. I_el=3.5 A.

Flat

Concave

Convex

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

J (

A/c

m^

2)

R (mm)

Radial distribution of the emission current density from the el. gun with flat cathodes 25 mm for I_el=3.5 A

Jemit4

Jemit1

0.0

2.0

4.0

6.0

8.0

10.0

12.0

2.0 2.2 2.4 2.6 2.8 3.0

Max

imu

m t

ran

sver

se e

ner

y, e

V

M field, kGs

Dependence of maximum transverse electron energy on uniform magnetic field for electron guns with cathodes diam. 25mm with different curvature

radii. I_el=3.5 A

Convex

Concave

Flat_1

Flat_4