Открытые вопросы в динамике охлаждённых пучков

Unsolved problems at the dynamic of the cooled beams

IX Международный семинар по проблемам ускорителей заряженных

частиц памяти В.П.Саранцева, 17 - 21 сентября 2011, Алушта,

Украина

Пархомчук В.В.ИЯФ СОРАН, Новосибирск

NAP-M storage ring pioneer of the storage rings with electron cooling

CELSIUS cooler

CSRe cooler

CSRm cooler

LEIR cooler

Coolers photo: The electron cooling experiments was made at this coolers and will used for discussion at this report

incomingIon beam

ExitIon beam

Cooling sections

Coherent dumping

)ln()/(

4

min

max31

cV

cnrr eie

Ai

Zirr pi

2

Single particle cooling rate

NN *1 The cooling rate of the fluctuation with N number of ion. cooling time single ion 1 sec cooling time for micro bunch with N=1.0E6 1 micro sec.

Sketch of Mg jet profile meter

Measuring the ion beam density at the center of beam versus time.Initially high (but negative) signal of cooled beam after kick close to 0 signal of wide profile and then cooling with returning to almost the same density

Without cooling linear increasing radius of the ion beam proportional of the amplitude of the kicker voltage/ But with the electron cooling on the radius after kick few times less!

For small proton current the amplitude return to value close to radius without coolingВлияние протонного тока на амплитуду раскачки после удара инфлектором 5 кВ. Протонный ток именялся от 55 мкА до, примерно, 1 мкА, а амплитуда от 2 мм до 5 мм.

1 0.5 0 0.5 1

5 104

0

5 104

vxnt j

xnt j

1 0.5 0 0.5 1

5 104

0

5 104

vxnt j

xnt j

1 0.5 0 0.5 1

5 104

0

5 104

vxnt j

xnt j

1 0.5 0 0.5 1

5 104

0

5 104

vxnt j

xnt j 1 0.5 0 0.5 1

5 104

0

5 104

vxnt j

xnt j

0 0.001 0.002 0.003 0.004 0.0050

0.5

1

1.5

Eck

k

f010

The phase space the ion beam after coherent kick.We can see the de coherent motion with decay average <x> and <vx> signal. Landay damping

0 200 400 600 800 1000 12000

0.2

0.4

0.6

0.8

1

1.2

dec=0dec=0.001dec=0.002dec=0.004dec=0.01dec=0.02

single particle (average) emittance

Dk 1

D1k 1

D2k 1

D3k 1

D4k 1

D5k 1

nturnk

0 200 400 600 800 1000 12000

0.2

0.4

0.6

0.8

1

dec=0dec=0.001dec=0.002dec=0.004dec=0.01dec=0.02

Coherent emitanse versus turns

Dk 2

D1k 2

D2k 2

D3k 2

D4k 2

D5k 2

nturnk

Coherent motion emittance decreased by mixing without coherent dampingSingle particle emittance are constant

But if coherent motion are cooled faster then mixing the rest single particle emittance decreased.

The fast electron beam energy modulation increased momentum spread of ion beam and the ion beam radius increased by more fast decoherence the ions oscillations.For Амплитуда колебаний в зависимости от амплитуды модуляции продольной скорости электронного пучка. Ep=65 MeV, Je=400 mA.

The intensity of the proton beam versus time with cooling and without cooling.As easy to see the first stage decay not change exist cooling or not exist (detune energy electron beam).

0 10 20 30 40 501E-3

0,01

0,1

1

10CELSIUS (1998) Je=200mA, Ue=25 kV

high intensity middle low

Pro

ton

bea

m c

urr

ent

(mA

)

time (s)

But decreasing initial intensity ion beam lead to absent initial fast decay..

LEIR accumulation Pb+54Positive influence the ion beam Inteancity. More intensive ion beam cooled faster.Initial hot ion beam after mixion with coled ion beam becames byIntra Beam Scatering more cool and more easy cooled by the electron coolingAt figure time increase down and between marks interval 1 s.The horizontaly the ion beam aperture 50 mm.Red painting is the electon beam profile for coolong.

0 0.2 0.4 0.6 0.8 1 1.2

0

1

2

3

4

time usec

sign

al f

rom

pic

kup

V3.341

0.1

yk j

1.0220 k dt

Рис.7. Прямое наблюдение сигналов на пикапе при группировке 200 МэВ/н при электронном охлаждении. Показаны первые 700 сек охлаждения, во время которых наблюдаются образование нескольких паразитных сгустков и довольно быстрые потери пучка.

The bunching carbon beam at CSReAfter injection on energy 200 MeV/u.Initially un bunching beam produceA many small micro bunches together withForming main bunch.

The history of the bunched electron cooling 200 MeV/u carbon beam at CSRe.At initial moomnt we can see fast decay intensity. But after decrease peak current2.5 mA the life times increased up to 1000 sec.

At initial cooling clear see micro structure of the ion beam current

But after final cooling all parasitic bunches disappeared. Maximal peak current near 3 mA.Clear see the tail of the ion bunch.

The intensity of the ion beam high for strong compensation accelerated RF field.

The pulse width is 10ms. The intervals related to left and right panel are 80ms and 100ms, respectively.”

0 100 200 300 400

100

Ion

beam

cur

rent

(A

)

Time (s)

100V

200V

400V

The ion beam intensity vs. time for the pulse height of 100V (best lifetime), 200V and 400V (worst lifetime), respectively. The pulse width is 20ms and the interval between two pulses is 100ms. The vertical axis is logarithmic. The dash line connected the beginning and the end of the data for the pulse height of 400V is for reference.

Working with detune (partially)Electron beam date was sended to meFrom IMP Lanzow colleges 11 Sept.

)(4

,

,

2

2

2

2

iienp

pi

e

pi

i

xnxneE

Em

e

dt

xd

EM

eZ

dt

xd

)sin()cos(1(21||3

22

4

22

pp

iep

p

ieA

The plasma model of the electron coolingCoherent oscillation

Заключение Как показывают многочисленные измерения пучков с

электронным охлаждением, эффекты интенсивности могут существенно улучшить или ухудшить свойства ионного

пучка. При использовании электронного охлаждения очень важно иметь это в виду и стараться создавать условия, когда эти особенности помогают решить поставленную

задачу.Взаимодействие ионного и электронного пучков еще плохо изучено с точки зрения когерентной устойчивости и ждет приложения усилий для дальнейшего развития методов

охлаждения.