Unsolved problems at the dynamic of the cooled beams охлаждённых пучков

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
Coolers photo: The electron cooling experiments was made at
this coolers and will used for discussion at this report
NAP-M storage
ring pioneer of
the storage rings with
electron cooling
CELSIUS
cooler
CSRe cooler
LEIR cooler
CSRm cooler
Cooling sections
Exit
Ion beam
incoming
Ion beam
Coherent dumping
4re ri ne c
 max
1 
 ln(
)
3
(V / c)
 min
Single particle cooling rate
2
Zi
ri  rp
Ai
N  1 * N
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
cooling
Влияние 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.
5 10
4
5 10
5 10
4
4
0
vxnt  j
0
vxnt  j
5 10
0
vxnt  j
4
5 10
1
0.5
0
0.5
5 10
4
4
1
xnt  j
1
0.5
0
0.5
1
1
0.5
0
xnt  j
5 10
0.5
1
xnt  j
4
5 10
4
0
vxnt  j
0
vxnt  j
5 10
4
5 10
1
0.5
0
xnt  j
0.5
4
1
1.5
1
0.5
0
0.5
1
xnt  j
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
1
Eck
0.5
0
0
0.001
0.002
0.003
k
f0
10
0.004
0.005
Coherent emitanse versus turns
single particle (average) emittance
1.2
1
1
0.8
Dk 1
Dk 2
D1k 1 0.8
D1k 2
D2k 1
D2k 2 0.6
D3k 1 0.6
D3k 2
D4k 1
D4k 2
D5k 1 0.4
D5k 2
0.4
0.2
0.2
0
0
0
200
400
600
nturnk
dec=0
dec=0.001
dec=0.002
dec=0.004
dec=0.01
dec=0.02
800
1000
1200
0
200
400
600
800
1000
nturnk
dec=0
dec=0.001
dec=0.002
dec=0.004
dec=0.01
dec=0.02
Coherent motion emittance decreased by mixing without coherent damping
Single particle emittance are constant
But if coherent motion are cooled faster then mixing the rest single particle
emittance decreased.
1200
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).
Proton beam current (mA)
10
CELSIUS (1998)
Je=200mA, Ue=25 kV
high intensity
middle
low
1
0,1
0,01
1E-3
0
10
20
30
40
50
time (s)
But decreasing initial intensity ion beam lead to absent initial fast decay..
LEIR accumulation Pb+54
Positive influence the ion beam
Inteancity. More intensive ion
beam cooled faster.
Initial hot ion beam after mixion
with coled ion beam becames by
Intra Beam Scatering more cool
and more easy cooled by the
electron cooling
At 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.
3.341
4
The bunching carbon beam at CSRe
After injection on energy 200 MeV/u.
Initially un bunching beam produce
A many small micro bunches together with
Forming main bunch.
signal from pickup V
3
yk  j
2
1
 0.1
0
0
0
0.2
0.4
0.6
kdt
time usec
0.8
1
1.2
1.022
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 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 current
2.5 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.
Ion beam current (A)
100V
200V
100
400V
0
100
200
300
400
Time (s)
Working with detune (partially)
Electron beam date was sended to me
The pulse width is 10ms. The intervals
related to left and right panel are 80ms and From IMP Lanzow colleges 11 Sept.
100ms, respectively.”
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.
d 2 xi Z e

Ep,
2
Mi
dt
The plasma model of the electron cooling
Coherent oscillation
d 2 xe
e

Ep,
2
mi
dt
E p  4e(nn xe  ni xi )
e2i2
e2i2
| A | 1  2
(1  cos( p ) 
sin(  p )
 p4
 3p
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.