Gaussian TEL gun progress

V. Kamerdzhiev, G. Kuznetsov, V. Shiltsev

LARP Collaboration Meeting 10Danfords on the Sound, Port Jefferson, NY, April 23-25, 2008

V. Kamerdzhiev for BBC team Gaussian TEL gun progress 2

The e-gun designThe electrode geometry is optimized for generating Gaussian-like transverse current density distributions (profiles) using SuperSam/UltraSam code*

* M. Tiunov, INP Novosibirsk, Russia

anode

control electrode (CE)

cathode

V. Kamerdzhiev for BBC team Gaussian TEL gun progress 3

The electron gun

assembled on a6 ¾ conflat flange

V. Kamerdzhiev for BBC team Gaussian TEL gun progress 4

The test bench

gun solenoid

main solenoid

collector solenoid

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Profile measurement technique

I = const

the deflector current is ramped in small steps

at every stepthe probe currentis recorded

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Electron beam analyzer

0.2 mm hole the current probe

ADC PC

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3D current density distribution @ 8kV

-4 -2 0 2 4

-4

-2

0

2

4

Horizontal deflector current (A)

Ve

rtic

al d

efle

cto

r cu

rre

nt (

A)

0.010000.088440.16690.24530.32370.40220.48060.55910.63750.71590.79440.87280.95121.0301.1081.1871.265

-4

-2

0

2

4

0.0

0.3

0.6

0.9

1.2

-4

-2

0

2

4Pro

be v

olta

ge (

V)

Verti

cal d

efle

ctor

cur

rent

(A)

Horizontal deflector current (A)

Ucath

= -8kV

Uce

= -8kV

Uanode

= -8.35kV, Gnd

Bgun

= 1.5kG

Bmain

= 2kG

Bcol

= 1.5kG

F = 65HzPW = 4s

Gaussian electron gun0.4'' cathode

Current densitydistribution

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Profiles vs Uce @ Ucath= 5kV

-5 -4 -3 -2 -1 0 1 2 3 4 5

0.0

0.5

1.0

1.5

2.0

2.5

P

robe v

olta

ge (

V)

Vertical corrector current (A)

-4.6kV -4.7kV -4.9kV -5kV -5.2kV -5.4kV

V. Kamerdzhiev for BBC team Gaussian TEL gun progress 9

Maximum ratings

-2.0x10-6 0.0 2.0x10-6 4.0x10-6 6.0x10-6 8.0x10-6

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Ele

ctr

on c

urr

ent (A

)

Time (s)

Imax

= 1.65AU

cath= U

ce= -10kV

Uanode

= -Ucath

, Gnd

Ucath = -10kV; Uanode = Ucath, Gnd; Ipeakmax = 1.65A; @ Bgun = 4kG; 5*10-9 Torr

The rise/fall time is defined by the driver circuit. Applying positive voltage to the CE in respect to the cathode will result in higher peak electron current

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Summary

• The Gaussian electron gun was successfully tested on the test bench at up to 10kV

• What to do next– install the Gaussian e-gun in one of the TELs– since the e-p beam alignment is very critical we need

to figure out the best way to achieve/maintain optimum e-p alignment

• the Digital Tune Monitor seems to be the best candidate capable of detecting the tune spread change (work in progress)

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Backup slides

• proposed hollow electron beam for LHC collimation system– e-gun simulations are performed using UltraSam code – simulations done by L. Vorobiev– mechanical considerations by G. Kuznetsov

• goals– keep the transverse electron energy low– extract as much current as possible– simulate e-beam compression in solenoidal magnetic field

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Hollow e-beam for LHC collimation system

cathode

near cathode electrode

control electrodeanode

cylindrical symmetry

current density distribution (profile)

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Example 2

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Example 3

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Simulated profile comparison

-30 -20 -10 0 10 20 30

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

cu

rrent densi

ty (

A/c

m^2

)

R (mm)

the proton beam passes through the zero e-current area

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Summary

• the “hollow” gun can be simulated with the tools we have (Super/Ultra SAM)– first look shows promising results

• mechanical design looks doable

• the infrastructure for testing the gun (once it’s been built) is available

• we plan to continue the development and demonstrate the detailed design