Collimation Systems - GSI

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ICFA
-
HB2004

Lattice and Collimation System

for J
-
PARC

Presented by


Michikazu Kinsho

(Japan Atomic Energy Research Institute)



Core Members

A.Ueno, T. Okawa, F.Noda, K.Yamamoto (JAERI)

T.Yokoi, M. Tomizawa, S.Machida (KEK)

ICFA
-
HB2004

Presentation Outline

1.
Introduction


J
-
PARC Accelerator Complex


Strategies of Beam Loss Control


2.
Design Concept of Collimation System


How to collimate halo beam ?


3.
Collimation Systems


Beam Transport Line from Linac to 3GeV
-
RCS (L3BT)


3GeV Rapid
-
Cycling Synchrotron (RCS)


Beam Transport Line the RCS to 50GeV
-
MR (3
-
50BT)


50GeV Main Ring

4.
Summary


ICFA
-
HB2004

J
-
PARC Accelerator Complex


The major requirements


Provide the 1MW for spallation neutron


With a repetition rate of 25Hz


Pulse length less than 1
m
s
=

Several ten GeV for nuclear and particle physics experiments

ICFA
-
HB2004

Strategies of Beam Loss Control


Beam transport line.


To minimize beam loss at the injection area of the ring.


To Localize of beam loss.


L3BT : 1.2 kW, 3
-
50BT : 450 W @ Collimation region.


RCS & MR.


To remove the beam halo before acceleration.


To Localize of beam loss.


RCS : 4 kW, MR : 450 W @ Collimation area.

High Intensity proton accelerator



Small % beam

loss becomes big beam loss.


Very difficult to control the beam loss with low level.



Beam loss control = Localization of beam loss


The only measure we can take is to localize any of losses in a restricted area.

ICFA
-
HB2004

2. Design Concept of Collimation System


How to collimate halo beam ?


There are
4 collimation area

in J
-
PARC accelerators.


3 kinds

of collimation system.



-

L3BT type,
-

RCS&MR type,
-

3
-
50BT type.


ICFA
-
HB2004

How to Collimate Halo Beam ?


L3BT type.


Charge exchange method.









How to collimate the halo beam ?

(1)
The halo beam hits the carbon foils.

(2)
H
-

beam is converted to H+ or H0.

(3)
to be separated the halo beam from the core beam (H
-
) by dipole magnet.

(4)
halo beam is transported to beam dump
.


to RCS

Beam Dump

Dipole Magnet

Carbon Foil

H
-

beam

Core beam (H
-
)

Halo beam (H+, H0)

Beam Dump

H+

H0

ICFA
-
HB2004

How to Collimate Halo Beam ?


3
-
50BT type.


All halo beam

is scatted by scatter and its particles are collected at collector.


Phase space coverage completely by scatter.


have to be converted during one pass through the beam line.





RCS & MR type.


Almost all

halo beam is scatted and its particles are collected at collector.


Particles of
small loss momentum
could be circulated, after several
circulating they are collected at collector.



Beam

Scatted particle

Scatter

Collector

to the MR

Beam

Scatted particle

Scatter

Collector

circulating

Come

again

ICFA
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HB2004

3. Collimation Systems

3.1 L3BT line


Overview of the L3BT


Design Concepts of the L3BT


Twiss Parameters of the L3BT


Concept of Beam Collimation System


Beam Loss Distribution

4 collimation systems in J
-
PARC accelerators


Beam Transport Line from Linac to 3GeV
-
RCS (L3BT)


3GeV Rapid
-
Cycling Synchrotron (RCS)


Beam Transport Line the RCS to 50GeV
-
MR (3
-
50BT)


50GeV Main Ring

ICFA
-
HB2004

Overview of the L3BT

Straight Section

Scraper
Section

Arc Section

Injection Section

Beam Dump #1

Beam Dump #3

Beam Dump #2

Beam Dump
#4(b)

Beam Dump
#4(a)

RCS

Linac

-

After the Linac


400MeV beam passes through the linac to the RCS


-

For the requirements



the beam loss minimization


not only connect the linac to the RCS


but also modifies the linac beam to the acceptable


shape for the RCS

ICFA
-
HB2004

Design Concept of the L3BT


Straight section


to match the linac beam with the following line and there is 1
st

debuncher


to keep the continuity of the betatron oscillation from the final section of the
linac


Arc section


to avoid the influence of the space charge effect


Scraper section


installed transverse scraper to remove a transverse beam halo


2
nd

debuncher cavity is installed to suppress the momentum spread


Injection section


adjusts the transported beam to the requirements parameters of the RCS


ICFA
-
HB2004

Twiss Parameter of the L3BT

(1)

(2)

(3)

(4)

b
⡭(
=
⠱⤠)瑲慩杨琠獥c瑩潮
=

to be composed of the doublet
structure to keep the continuity of
the betatron oscillation

(2) Arc section


to be composed of three
DBA(Double Bens Achrimatic)
lattice to avoid the influence of the
space charge effect

(3) Scraper section


To be composed of simple FODO
cells

(4) Injection section


adjusts the transported beam to the
requirements parameters of the
RCS


h
⡭(
=
ICFA
-
HB2004

Concept of Beam Collimation System


Concept.


to minimize beam loss

at the injection area of RCS.


Collimation system.


Consists of adjustable carbon stripping foils and the beam dump.


How to collimate the halo beam.

(1)
The halo beam (blown up over 4
p

mm*mrad) hits the carbon foils.

(2)
H
-

beam is converted to H+ or H0.

(3)
to be separated the halo beam from the core beam (H
-
) by dipole magnet.

(4)
halo beam is transported to beam dump.

to RCS

Beam Dump #4(a)

Dipole Magnet

Carbon Foil

H
-

beam

Core beam (H
-
)

Halo beam (H+, H0)

Capacity : 2 kW

Capacity : 600 W

Beam Dump #4(b)

Estimated beam loss :1.3 kW

ICFA
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HB2004

Beam Loss Distribution


The beam losses distribution.


along the scraper section and beam dump line.


The beam loss distribution was estimated by STRUCT code.


There are 8 scrapers. ;
Horizontal : 4 sets, Vertical : 4 sets.


45degrees x 4 sets respectively.

Q magnet

Carbon foil (Scraper)

Dipole

magnet

Beam

dump

ICFA
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HB2004

3.2 RCS Collimation System

3.2 RCS


Overview of the RCS


Concepts of Collimation System


Two Stage Collimation System


Location of the Collimation System


Beam Halo Distribution


Assumption for calculation


Beam Loss Distribution


Collimation Efficiency


Residual Dose at Collimator

ICFA
-
HB2004

Overview of the RCS


Localization of beam loss


Collimation area

:
4 kW


Injection area

:
1 kW


Extraction area

:
1 kW


Another area

:
1 W/m


for hands on maintenance




Collimation system


With High Collimation Efficiency

ICFA
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HB2004

Two Stage Collimation System

• Transverse and longitudinal collimation system is prepared.

• Two
-
stage collimation system




consists of
3 primary

(for scatter) and
5 secondary

(for collector) collimators



Every primary collimator


restricts the apertures to
324
p
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ㄥ=浯浥湴n洠摩d灥牳楯渮
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=

Physical aperture


other elements are larger than
486
p
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ㄥ=浯浥湴n洠摩d灥牳楯p
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r
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p
o
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e
a
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>
3
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.
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P
/
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>
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%
偲業慲y
=
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=
Collimator

Beam envelope

324
p
=
浭m浲慤
=
V慣畵洠a楰i
=
Q
-
magnet

Q
-
magnet

Beam Halo

e
=
>=㌲㑰洮浲慤
=
/
D
p
/
p⼠>‱‥
=
ICFA
-
HB2004

Location of the Collimation System

100
150
200
250
300
350
400
0
5
10
15
20
25
30
Quadrupole magnet
Dipole Magnet
Longitudinal primary collimator
{
Transvers primary collimator
Secondary collimators
Injection point
b
,
h
[m]
S [m]

b
x


b
y


h
x


The transverse primary collimators


are located in the half of the injection

straight section


The longitudinal primary collimator


is set
at

the dispersion maximum point upstream of the transverse primary collimators.


The secondary collimators


are located in the half of the injection

straight section

ICFA
-
HB2004

Beam Halo Distribution

Transverse Halo

Longitudinal Halo


Transverse halo


Emittance : 324
p

to 364
p

mm.mrad, and longitudinal distribution : +
-

1 %


Longitudinal halo


Longitudinal off momentum : 1% to 1.5%, and transverse emittance : 324
p

mm.mrad

ICFA
-
HB2004

Beam Loss Distribution

The beam loss could be localized
in the collimator region



98.8%

for the transverse collimation,


97.6%

for the longitudinal collimation

in the calculations.

0
50
100
150
200
250
300
10
-1
10
0
10
1
10
2
10
3
10
4
10
5
Loss [W/m]
S [m]
Collimator Region

Injection Point

ICFA
-
HB2004

Collimation Efficiency


At R=1.5.

e

:
almost 99% and saturated

for transverse.

e

:
not saturated

for longitudinal.


but
e=97.5%.




e
=
景f潮杩瑵摩湡t.
=
††††
is saturated when
R becomes 2.



Big R
-
value.


is extension
cost.

Collimation Efficiency :
e
==坣W⼠坴
=
======
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=
======
坴W㨠瑯瑡氠扥慭b汯獳⁩渠w桯汥h物湧

1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
70
75
80
85
90
95
100
Physical aperture ratio
Collimation efficiency [%]
Longitudinal Collimation efficiency
Transverse Collimation efficiency
R: ring / collimator acceptance ratio

e

: Collimation Efficiency [%]

Present design :
R=1.5

ICFA
-
HB2004

Residual Dose at Collimator



Calculation result of MARS code



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ㄠ摡1 捯c汩湧



Collimator :

ㅓ1⽨

䥲潮o獨楥汤l㨠

㄰浓瘯栬



Concrete shield :

100μSv/h

C
u
p
p
e
r

C
o
l
l
i
m
a
t
o
r
I
r
o
n

S
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r
V
a
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m

C
h
a
m
b
e
r
Cupper Collimator

Iron Shield

Beam Center

Vacuum Chamber

Concrete Shield

mSv/hr.

100

10

1

1000

Beam Center

ICFA
-
HB2004

3.3 3
-
50BT Collimator System

3.3 3
-
50BT


Overview of the 3
-
50BT line


Concepts of Collimation System


Two Stage Collimation System


Location of the Collimation System


Beam Loss Distribution


Two cases of beam loss at collimator

ICFA
-
HB2004

Overview of 3
-
50BT


Design conditions.


Beam from the RCS is divided into 2 beam lines by pulse bending magnet ;
one goes to the neutron and muon production target, the other goes to MR.


To collect beam halo, beam scrapers and collectors are installed as much as
in the upstream. (called scraper section.).


The beam scraper section consists of three normal cells, and to perform
effective beam scraping, each phase advance is set as 120 degrees.


Since a 4.3 m difference is in the level of the RCS and the MR, the 3
degrees slope section is prepared.


A radiation shield wall is installed between a slope section and a scraper
section. Total beam loss is estimated 450 W at scraper section.


Twiss parameters at the injection point of the MR should be matched.

ICFA
-
HB2004

Concept of the Collimation System


All halo beam

is scatted by scatter and its particles are collected at collector.


Phase space coverage completely by scatter.


have to be converted during one pass through the beam line.


Beam

Scatted particle

Scatter

Collector

to the MR

Phase space coverage of the beam scraper



3 scrapers for vertical and 3 scrapers for
horizontal could be cover completely.


ICFA
-
HB2004

Location of the Collimation System

Lattice functions of the 3
-
50 beam transport line.

Top figure is
b
=
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=
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=
Slope section

ICFA
-
HB2004

Beam Loss Distribution


About 2 % (max. 5%) of
the scattered particles
reach to exit of BT line.



5~6 % of the scattered
particle hit the Q
-
magnet.

Typical Results of the tracking for beam scraping


-

case 1 : all halo beam hit the scraper #3


-

case 2 : all halo beam hit the scraper #6

Case 1

Case 2

Collimation system


works well !

ICFA
-
HB2004

3.4 MR Collimator System

3.4 MR


Concepts of Collimation System


Location of the Collimation System


Residual Dose at Collimator

ICFA
-
HB2004

Concept of the Collimation System for the MR


The role of the beam collimation.


to remove the beam halo before beam acceleration.


The collimator acceptance.


between
54
p

and 81
p

mm.mrad at injection energy (3GeV).


The total beam loss.


estimated
450 W

at the scraper section.


Design of the scraper.


Two points were considered. One is the beam loss should be localized, and
the other is the aperture must be adjusted after installation.


ICFA
-
HB2004

Location of the Collimation System

(1)

(2)

(3)

(1)
Injection section

(2)
Scraper section

(3)
Abort section

Scraper section

Lattice functions of the MR. Top figure is
b
=
晵湣瑩潮猠慮搠扯瑴潭=潮攠楳i
摩獰敲獩潮=晵f捴c潮s⸠†.潬楤=汩湥⁩猠景r⁨潲oz潮瑡t=慮d⁤慳桥搠汩湥n楳if潲⁶敲瑩t慬a
=
ICFA
-
HB2004

Residual Dose Distributions

Residual dose distributions.


1 year irradiated, and 1month cooling.


the aperture of scraper :
56
p

mm.mrad.


collector :
70

p

mm.mrad,


almost all loss particle could


be localized in collimator region.

Residual Dose


not so high !

downstream

upstream

Residual Dose (mSv/h)

Distance (m)

ICFA
-
HB2004

Summary 1


In

order

to

localize

beam

loss
.


several

kinds

of

beam

collimation

system

are

prepared

in

the

J
-
PARC

accelerators
.


In

L
3
BT

line
.


beam

collimation

system

which

is

used

for

8

carbon

foils

and

beam

dump

is

prepared

to

minimize

the

beam

loss

at

the

injection

area

of

the

RCS
.


Almost

all

of

H
-

halo

beam

could

be

converted

to

H+

beam

after

passing

through

the

carbon

foils

and

be

transported

to

beam

dump

in

this

system
.


In

the

RSC
.


two
-
stage

collimation

system

is

prepared

to

localize

beam

loss

in

this

collimation

system
.


The

ratio

of

physical

aperture

and

collimator

acceptance

is

decided

1
.
5

because

collimation

efficiency

becomes

about

98

%

and

this

values

is

still

saturated
.

ICFA
-
HB2004

Summary 2


In

the

3
-
50
BT

line
.


beam

collimation

system

which

is

used

for

scatter

and

collector

is

prepared

to

minimize

the

beam

loss

at

the

injection

septum

magnet

of

the

MR
.


Since

there

are

6

scatters

and

3

collectors

in

this

system,

only

0
.
2

%

scattered

particle

could

reach

to

the

injection

septum

magnet

of

the

MR
.


In the MR.


two
-
stage collimation system is also prepared to remove the beam halo
before beam acceleration.


In the case that the aperture of scraper is set 56
p

mm.mrad and collector is
set 70
p

mm.mrad, almost all loss particle could be localized in collimator
region.


From the calculation results,


every collimation system works well !

ICFA
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HB2004

Solenoid field is 30 G.

The effect of secondary electron

production is included.

Electron cloud build
-
up (calculated by Ohmi)


e
-
production rate < 4*10
-
6
/(m.p)

1.7*10
-
4
/(m.p) at collimator.

Solenoid is necessary for cure.

(by Toyama at ’ecloud04’)

=>

Uncontrolled rate is

3.4*10
-
6
/(m.p).

Beam is stable.

ICFA
-
HB2004

Remote Handling System

Remote Handling System for the Vacuum Flange


Collimator vacuum chamber can be removed only by turning the screws far from this
system. One screw open the quick
-
coupling clamp and another screw separate each flanges.
Improvement of prototype is on
-
going.

ICFA
-
HB2004

Impedance measurement


To reduce the impedance of the
collimator, we insert the taper
ducts and the RF contacts in the
collimator chamber.


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灥牦潲o敤e批 瑨攠w楲攠浥瑨潤
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浥慳ar敤e瑨攠汯湧楴畤楮慬i
Impedance.

Extraction
Injection
n
Z
L
@
28
.
0
@
20
.
0




 
  
 


Criteria

420Ω@Injection


6.6Ω@Extraction


are cleared