LEIR Schottky system and Experimental Results J.TAN AB/BDI

Jocelyn TAN CERN AB / BI 11 Dec. 2007 CARE

LEIR Schottky system and

Experimental Results

J.TANAB/BDI


Outline

1. LHC ion injector chain

2. LEIR • Machine• Schottky Pick-Ups

3. Commissioning with :• Oxygen ions O4+

• Lead ions Pb54+

4. Summary


LHC Filling Scheme : Pb54+ ions

ECR

RFQ LINAC3

SPSPS

LHC

LEIR

4.2 MeV/u, =0.095

rep. rate 1 to 5Hz Energy ramping cavity p/p~0.4%

Pb27+ Pb 54+

•stacking of 9x108 ions at 4.2 MeV/u•accel. to 72 MeV/u•2 bunches of 4.5x108 ions each•cycle length 3.6s

*accel. to 5.9 GeV/u *Double bunch splitting

*4 pairs of bunchlets per 3.6s

~13 PS inj./ SPS cycle

1 ej./1. mn at 177GeV/u

592 bunches ~10mn filling time per ring.

7.107 /bunch 2.76TeV/u, L = 1027 cm-2 s-1

200 eA

Pb 27+

Pb82+ Pb 54+


LEIR Machine (1)

Square-shaped machine

Two-fold symmetry

With electron cooler

78.54 m Circumference

0.095 - 0.37 Relativistic

0.36 – 1.42 MHz Rev. frequency

1.82 / 2.72 QH / QV

10-12 Torr Vacuum

300 ˚C Bake out temp.

injection

ejection Nominal Lead Ions Cycle : 3.6s

0 500 1000 1500 2000 2500 3000 3500

t[ms]0.0

0.2

0.4

0.6

0.8

1.0

1.2

B[ T ]

multi-turn injection 200sMain dipole field [T]

Electron cooling + Stacking

4.2 MeV/u

Acceleration

72 MeV/u

Extraction

Injection repetition rate : 1 to 5 Hz

Beam unbunched for 1600ms

Schottky signals are essential for diagnostics and controlling phase-space cooling efficiency


LEIR Machine (2)

injection line

Electron cooler

extraction point


Stripline electrode

L

c

Lt

c

Lt

21

j

B ettI

fI )(2

sin2

)( 120

picking up the signal upstream the line

picking up the signal donwstream the line

j

A ettI

fI )(2

sin2

)( 120

Striplines electrodes

Z0 = 50

Matched lines

A B

A

Bt1 t2

t2+t1


LEIR : Travelling-Wave mode

• Travelling-Wave Striplines for low energy particles

delay delay

i0

3i0

2i0

P ~ (Nstripxi0)2


LEIR : Travelling-Wave mode

• Travelling-Wave Striplines for low energy particles

delay delay

delay delay

Hybrid

port port

Beam

Superposition of currents

Good S/N ratioTotal power ~ (Nstripi0)2


LEIR : Parallel combination

• Monitor backward signal : for high (any) energy particles

Hybrid HybridHybrid

Total power ~ Nstripxi02

delay1 delay2

Combiner

i0 i0 i0


Schottky Pick-Ups Layout

UCV22-TWINJECTION : Travelling Wave modeEXTRACTION : Parallel mode

Horizontal and Longitudinal : 24 pairs of stripline-electrodes

Vertical : 6 pairs of stripline-electrodes

Vertical : 8 pairs of stripline-electrodes

Horizontal and Longitudinal : 24 pairs of stripline-electrodes


-180

-170

-160

-150

-140

-130

-120

0.1 1 10 100 1000Frequency [MHz]

Sp

ec

tra

l p

ow

er

de

ns

ity

[d

Bm

/Hz

]

N=2.5x108 Lead ions

In the control room...

-70 dBm/Hznoise level of the spectrum noise level of the spectrum analyser = analyser = -140 dBm/Hz-140 dBm/Hz

-145 dBm/Hz

100th harmonic at 36 MHz

Pick-Up

Resolution BW = 1.5 kHzPeak signal = - 38 dBm ( i.e. 2.7 mV peak)

-45

-55

-65

-75

-85

-95

-105

75 dB

Inj. trigger

p/p = 4.10-3

reduced thermal noise = -177 dBm/Hz

Aug. 2007 : new Spectrum analysers + remote

desktop

N=2.25x108 Lead ions


Commissioning with O4+ ions : Oct.-Nov. 2005

Longitudinal plane Horizontal spectrum

(101-qh ).f0

(100+qh ).f0

99.f0 100.f0 101.f0

Expected longer vacuum life-time than with Lead ions (lower cross section for charge exchange processes with the residual gas)

O4+ and Pb54+ have very close Z/A Nearly same beam rigidity for both ion species

Results and observations

Vertical spectrum

(50-qv ).f0 (50+qv ).f0

50.f0

frev = 363.3 kHz

Injection momentum spread ~ 4x10-3

Qh = 1.795 Qv = 2.604

Unexpected shorter lifetime : vac. leaks + desorption

Fast losses coupled w/ transverse “activities” observed : coupling impedances ions trapped in potentials created by e- beam

Interpretation of beam cooling not straightforward


Spectrogram of the momentum cooling during stacking on the injection front porch. The vertical and horizontal axis denote time (1.6 s total from top to bottom); and momentum spread (1% full scale) respectively. There are 5 injections-cooling stacking sequences every 300ms

Commissioning with Pb54+ ions : 2006-2007 : Nominal Scheme

7.8x108 cold ions before bunching

~30% off wrt

Nominal value


MOMENTUM

full span is equivalent to p/p = 1%


VERTICAL

full span is equivalent to p/p = 1%


Summary

Schottky system in LEIR is fully operational

GUI displaying e.g. tune vs time is expected for the next run

The pick-ups for high momentum have been commissioned, but never used


Evolution of beam dimensions during Evolution of beam dimensions during injection and cooling processinjection and cooling process

PERFORMANCES :NOMINALPERFORMANCES :NOMINAL

Courtesy M. CHANEL, G. TRANQUILLECourtesy M. CHANEL, G. TRANQUILLECourtesy M. CHANEL, G. TRANQUILLECourtesy M. CHANEL, G. TRANQUILLE

30

20

10

0

Sigma[mm]


Putting numbers : injection

Number of particles 2.25x108 ions

In all formula, replace “e” by “Ze”

Qh / Qv 1.82 / 2.72

Betatron function h/v = 6.5 / 5.5

Striplines geometry 16cm/13cm

Transfer function

Injection Ejection

Energy/n[MeV/n]

4.2 72.2

Revolution frequency

360kHz 1.422 MHz

0.863 0.734

relativistic 0.0947 0.3725

p/p4x10-3

10-32x10-3

h/v norm. 1

[.m]

1.7 / 1 0.3/0.25

0.7 / 0.7


0

100

200

300

400

500

600

0.1 1 10 100 1000Frequency [MHz]

Sch

ott

ky C

urr

ent

No

ise

[p

A/H

z1/2 ] N=2.25x108 Lead ions

Injection: Longitudinal spectrum

1010NF

eq

R

kT

Injection

After e-cooling

6


-110

-100

-90

-80

-70

0.1 1 10 100 1000Frequency [MHz]

Sp

ec

tra

l po

we

r d

en

sit

y [

dB

m/H

z ]

N=2.25x108 Lead ions

Injection : Transverse spectra

Horizontalh= 0.3 .mh= 1.7 .m

Verticalv= 0.25 .mv= 1 .m


R, T iR(f)ideal

Equivalent input noise (1)

Johnson noise of a resistor:

]/[ 4

)( HzAR

TkfiR

R

real

real world equivalent circuit

)110( 10 NF

eq TT

Noise Figure of an amplifier : NF [dB] Passive components Transistors : Shot noise FETs : voltage and current noise Equivalent noise source

real+

GRin Teq

realRs

real

Equivalent input noise

]/[ 10

)(10

HzAR

TkfI

s

NF

eq

idealxGIeq(f)

Rs, Tideal


Ieq (f)

Equivalent input noise (2)

293K 10.3

LN2 5.3

10K 1.9

50 Load

Eq. Noise Ieq(f)[pA/Hz1/2]

With active loads the input noise isdecreased by ~-6dB

Zin = 50NF1 = 1.2 dB NF1 T = Room Temp.

Teq = 93K

Low Noise Amplifier

)110( 101

NF

eq TT

+G

Rin Teq

]/[ 10

)(10

HzAR

TkfI

s

NF

eq

5.8

Te

q

LNANF

LNANF1

Documents

LEIR Schottky system and Experimental Results J.TAN AB/BDI