High-Density
the CERN
CERNPS
PS
High-Densityand
andHigh-Intensity
High-Intensity Beams
Beams at the
High-Density and High-Intensity Beams at the CERN PS
R. R.
Cappi,
M.M.
Giovannozzi,
A.-S.Muller,
Muller,
Cappi,
Giovannozzi,M.
M.Martini,
Martini,E.
E.Metral,
Métral, G. Metral,
Métral, A.-S.
R. Cappi, M. Giovannozzi, M.
Martini,
E.
Métral,
G.
Métral,
A.-S.
Muller,
R.R.Steerenberg
Steerenberg
R. Steerenberg
CERN
PSPS
Division,
CERN
Division,1211
1211Geneva
Geneva23,
23, Switzerland
Switzerland
CERN PS Division, 1211 Geneva 23, Switzerland
Abstract.
TheThe
production
of of
high-density
and
activityatatthe
theCERN
CERNProton
Proton
Abstract.
production
high-density
andhigh-intensity
high-intensitybeams
beams has
has been
been a constant
constant activity
Abstract.
The
production
of years.
high-density
and
beams
been situation,
a constantincluding
activity at
thea aCERN
Proton
Synchrotron
(PS)
since
many
This
paper
statusreport
report
thehas
present
also
discussion
ofof
Synchrotron
(PS)
since
many
years.
This
paper
is ishigh-intensity
a astatus
ofofthe
present
including
also
discussion
Synchrotron
(PS)and
since
many
years. This paper is a status report of the present situation, including also a discussion of
ongoing
studies
future
activities.
ongoing
studies
and
future
activities.
ongoing studies and future activities.
INTRODUCTION
INTRODUCTION
INTRODUCTION
HIGH-DENSITY BEAMS
HIGH-DENSITY
BEAMS
HIGH-DENSITY
BEAMS
The Nominal LHC Beam
Nominal
LHC
Beam
TheThe
Nominal
LHC
Beam
The beam parameters of the nominal LHC beam
12
beam
parameters
nominal
LHC
beam
are The
[1]:
Nt parameters
8×10
ppp
,the
ε∗the
3 µm.
Thisbeam
The
beam
of 2of
nominal
LHC
x,y
∗
12 12 ppp
2PS2performance
are
[1]:
N
8×10
,
ε
3
µm.
This
beam
density
exceeds
typical
by
more
that
a
are [1]: Nt ~ t 8xl0 ppp , e*x?y x,y
< 3 jim. This beam
density
exceeds
typical
PS
performance
by
more
that
factor
of
two.
The
nominal
figures
can
be
achieved
density exceeds typical PS performance by more that a a
factor
ofapplying
two.
nominal
figures
achieved
only
some
special
manipulations:
i) inject
factor
of by
two.
TheThe
nominal
figures
cancanbebeachieved
two,
instead
ofsome
one,
PS-Booster
(PSB) pulsesi) into
the
by
applying
some
special
manipulations:
i)inject
inject
onlyonly
by applying
special
manipulations:
PS
(i.e.
doubling
thePS-Booster
final value
for N
whileinto
keeping
instead
of one,
(PSB)
intothe
the
t pulses
two, two,
instead
of
one,
PS-Booster
(PSB)
pulses
∗
PS
(i.e.
doubling
the
final
value
for
N
while
keeping
ε
unchanged);
ii)
avoid
any
emittance
dilution
t
x,y doubling the final value for Nt while keeping
PS (i.e.
∗
The double-batch
injection
process
is dilution
shown
in
avoid
emittance
dilution
x,y unchanged);
e*x?y εeffect.
unchanged);
ii) ii)
avoid
anyanyemittance
Fig.
1.
effect.
The
double-batch
injection
process
is
shown
effect. The double-batch injection process is shown inin
Fig. Fig.
1. 1.
Second batch injection
500
1
The relevant parameter is the particle flux, Nt f with f the repetition
machine
cycle
length
will be
considered.
the
particle
flux,
Nt f with
f the
repetition
Therate.
relevant
parameter
isfixed
the machine
particle
flux,
Nlength
f the
repetition
ForFor
thesimplicity,
so-called aultimate
LHC beam
the
intensity
increases
to
t f with
cycle
will
be
considered.
13
rate. For
a fixed
machine
cycle
length
will
be considered.
2Nt simplicity,
ppp
keeping
the LHC
same
transverse
For1.3×10
the so-called
ultimate
beam
the emittances.
intensity
increases to
2
ForNthe1.3×10
so-called
beam
the intensity
increases to
13
pppultimate
keeping LHC
the same
transverse
emittances.
1
t
Nt ~ 1.3xl013ppp keeping the same transverse emittances.
1500
2000
2500
FIGURE 1. PS intensity versus time. The double-batch
FIGURE
PS
intensity
versus time.
time. The double-batch
FIGUREis1.1.
PS seen
intensity
versus
injection
clearly
as a step
increase. The double-batch
injection
increase.
injectionisisclearly
clearly seen
seen as
as aa step
step increase.
The two injections at 1.4 GeV kinetic energy are
The
two
at
1.4 GeV
GeV kinetic energy
energy are
Thevisible,
two injections
injections
at 1.2
1.4
clearly
spaced by
s (thekinetic
repetition rate are
of
clearly
visible,
spaced
by
1.2
s
(the
repetition
rateofof
clearly The
visible,
by 1.2 s is
(thepractically
repetition 100%;
rate
PSB).
totalspaced
transmission
PSB).
transmission
is practically
practically
100%;
PSB). The
The total
total
transmission
is
100%;
neither
losses
nor emittance
blow-up
occur during
the
neither
losses
nor
emittance
blow-up
occur
during
the
neither
losses flat-bottom.
nor emittance blow-up occur during the
long
injection
long
longinjection
injection flat-bottom.
flat-bottom.
The evolution of ε∗ x,y along the PS cycle, from PSB
The
of
along
the PS
PS
cycle,
fromPSB
PSB
Theevolution
evolution
of e*
ε∗x?y
the
from
extraction
to PS extraction
and also
in cycle,
the
transfer
line
x,y along
extraction
to
PS
extraction
and
also
in
the
transfer
line
extraction
to
PS
extraction
and
also
in
the
transfer
line
between the PS and the Super Proton Synchrotron
between
PS
Proton Synchrotron
Synchrotron
between
the
PSinand
and
the
(SPS)
arethe
shown
Fig.the
2. Super Proton
(SPS)
(SPS)are
are3.5shown
shown in
in Fig.
Fig. 2.
Outside specifications
3.5
3.0
PS injection (second
batch) specifications
Outside
3.0
2.5
PS injection (second batch)
2.5
2.0
PS extraction
2.0
1.5
1.0
1.5
1.0
0.5
PS injection (first batch)
Transfer line
PS extraction
PSB
PSoutput
injection (first batch)
line 64)
x (section 54) Transfer
x (section
y (section 75)
y (section 85)
x (section 54)
x (section 64)
y (section 75)
y (section 85)
PSB output
0.0
0.5
0.0
0
500
1000
1500
2000
2500
Time (ms)
0
1rate. For simplicity, a fixed
The relevant parameter is
2
1000
Time (ms)
*
εµx,m)
µm)
y (µ
x, y (µ
Although the longitudinal emittance εl is also an
Although
the the
longitudinal
emittance
81εisl number
Although
longitudinal
emittance
isalso
alsoanan
issue,
its value
being
dictated
by the total
of
issue,
its
value
being
dictated
by
the
total
number
ofof
issue,
its
value
being
dictated
by
the
total
number
bunches, their shape or length, collective effect
bunches,
theirtheirshape
or orlength,
effect
bunches,
shape
length,collective
collective
effect
considerations
and
also
hardware
limitations,
this
considerations
andand
also
hardware
limitations,
considerations
hardware
limitations,
this
paper focus mainly
onalso
transverse
beam
dynamics. this
paper
focusfocus
mainly
on on
transverse
beam
dynamics.
paper
mainly
transverse
beam
dynamics.
Extraction at 26 GeV/c
*
In the second set, only the total number of protons
In the
second
set,set,
only
thethe
total
number ofofprotons
In the
second
only
total
protons
Nt needs
to
be maximised.
The
PS number
normally delivers
Nt needs
to
be
maximised.
The
PS
normally
1 delivers
N
needs
to
be
maximised.
The
PS
normally
delivers
such
beams either for neutrino experiments
t
1 1, as is the
suchsuch
beams
for for
neutrino
experiments
, as
beams
neutrino
experiments
, asisSasso
isthe
the
case
of either
the either
future
CERN
Neutrino
to Gran
casecase
of
the
future
CERN
Neutrino
to
Gran
Sasso
of the
Gran Sasso
(CNGS)
beamfuture
[2], orCERN
for theNeutrino
neutron to
Time-of-Flight
(CNGS)
beam
[2],[2],
or or
forfor
thethe
neutron
Time-of-Flight
(CNGS)
beam
neutron
Time-of-Flight
(nTOF)
Facility
[3].
(nTOF)
Facility
[3].[3].
(nTOF)
Facility
First batch injection
ε
different
typesof ofproton
protonbeams
beamswill
will bebe
TwoTwo
different
types
Two indifferent
types
ofnamely
proton
beams willand
be
considered
in
paper,
high-density
and
considered
thisthis
paper,
namely
high-density
considered
in
this
paper,
namely
high-density
and
high-intensity
ones.
characterizedbyby
high-intensity
ones.
TheThe
firstfirst
setsetis ischaracterized
∗
high-intensity
ones. NThe
first
set is Ncharacterized
by
having
a large
, where
number
b is
having
a large
ratioratio
Nb / be*/x,εy∗, x,ywhere
N
thethenumber
b is
∗
having
a largeper
ratiobunch
Nb / ε and
N
is
the
number
x,y, where
b
of
protons
ε
the
normalized
of protons per bunch and e*x?y∗x,ythe normalized
of
protons(horizontal/vertical)
per bunch and ε x,y emittance.
the normalized
transverse
transverse
(horizontal/vertical) rmsrms
emittance. AsAsanan
transverse
(horizontal/vertical)
rms
emittance.
As PS
an
example,
the
nominal
LHC
beam
generated
the
example,
the the
nominal
LHC
beam
generated
byby
the
PSPS
example,
nominal
LHC
beam
generated
by
the
[1]
falls
in this
category,thethehigh-density
high-densitybeing
being aa
[1] [1]
fallsfalls
in this
category,
in
this
category,
the high-density
being a
necessary
condition
for
achieving
the
high-luminosity
necessary
condition
for
achieving
the
high-luminosity
necessary
required bycondition
the LHC.for achieving the high-luminosity
required
by the
LHC.
required
by the
LHC.
FIGURE 2.
500
1000
1000
1500
1500
Time (ms)
Time
(ms)
Evolution of ε∗x,y along
measured
output,
Evolution atofPSB
ε∗x,y
along
xy
2000
2500
the PS cycle. The
emittances
are Evolution of e* , along in
PScycle.
after The
the
FIGURE 2.2.
the
FIGURE
thethePS
PS
cycle.
The
1st
batch
injection,
before
and
after
the
2nd
batch
injection,
emittances
are
measured
at
PSB
output,
in
the
PS
after
emittances are measured at PSB output, in the PS afterthe
the
before
extraction,
and
in theand
transfer
theinjection,
SPS.
1stbatch
batch
injection,
before
after
the
2nd
1st
injection,
before
and
afterline
thetowards
2ndbatch
batch
injection,
beforeextraction,
extraction, and
and in
in the
the transfer
transfer line towards
SPS.
before
towardsthe
the
SPS.
Different instruments
are usedline
to measure
ε∗ x,y
. At
∗
PSB
extraction,
beam
emittances
are
obtained
Different
instruments
are
used
to
measure
ε
Different instruments are used to measure e*x,yx?y. by
.AtAt
means
of
SEM-grids
located
in
a
dedicated
PSB
extraction,
beam
emittances
are
obtained
PSB extraction, beam emittances are obtained byby
measurement
line. In the PS
ring, two
of wire
means of
of SEM-grids
SEM-grids
located
in
aa dedicated
means
located
in pairs
dedicated
scanners
(eachline.
performing
H/Vring,
plane
measurements)
measurement
In
the
PS
two
pairs
measurement line. In the PS ring, two pairs ofof wire
wire
are
located
in performing
different machine
sections. Finally,
scanners
(each
scanners
(each
performing H/V
H/V plane
plane measurements)
measurements)
SEM-wires
transfer line between
the PS and the
are locatedininthedifferent
are
located in different machine
machine sections.
sections. Finally,
Finally,
SPS
measure
thetransfer
extracted
SEM-wires
in the
line beam
betweenemittance.
the PS andThe
the
SEM-wires in the transfer line between the PS and the
SPS measure the extracted beam emittance. The
SPS measure the extracted beam emittance. The
CP642, High Intensity and High Brightness Hadron Beams: 20th ICFA Advanced Beam Dynamics Workshop on
High Intensity and High Brightness Hadron Beams, edited by W. Chou, Y. Mori, D. Neuffer, and J.-F. Ostiguy
© 2002 American Institute of Physics 0-7354-0097-0/02/$ 19.00
59
average
emittance
value
isiswell
the
33µm
average
emittance
value
wellbelow
below
the
|imlimit
limit
average
emittance
value
is well
below
the 3 µm limit
ininboth
planes,
with
an
accuracy
of
±
10
%.
both
planes,
with
an
accuracy
of
±
10
%.
in both planes, with an accuracy of ± 10 %.
AAnumber
ofofmodifications
ininthe
PSB/PS chain,
the
chain,
Anumber
number
ofmodifications
modificationsof
inbeam
the PSB/PS
PSB/PS
chain,
together
with
fine
adjustments
parameters,
together
with
fine
adjustments
of
beam
parameters,
together with fine adjustments of beam parameters,
had
to be applied toto achieve
the nominal
had
had toto bebe applied
applied to achieve
achieve the
the nominal
nominal
characteristics
of
the
LHC
beam
[4].
In
particular,
to
characteristics
of
the
LHC
beam
[4].
In
particular,
characteristics of the LHC beam [4]. In particular, toto
avoid
emittance
blow-up
during
the
1.2
s
long
avoid
avoid emittance
emittance blow-up
blow-up during
during the
the 1.2
1.2 ss long
long
flat-bottom,
three main
approaches were
used:
flat-bottom,
flat-bottom, three
three main
main approaches
approaches were
were used:
used:
i)i)increase
of the PSB
extraction energy
from 1 1toto
i)increase
increaseofofthe
thePSB
PSB extraction
extraction energy
energy from
from 1 to
1.4
GeV
to
reduce
the
space-charge
incoherent
1.4GeV
to
reduce
the
space-charge
incoherent
tune
1.4 GeV to reduce the space-charge incoherenttune
tune
shift
from
-3.5
to
-2.3;
ii)
transverse
higher-order
shift
from
-3.5
to
-2.3;
ii)
transverse
higher-order
shift from -3.5 to -2.3; ii) transverse higher-order
mode
head-tail
instabilities
mode
head-tail
instabilities
cured
the
PS
by
x-y
mode
head-tail
instabilitiescured
curedinininthe
thePS
PSby
byx-y
x-y
coupling
generated
with
skew
quadrupoles
[5];
iii)
coupling
generated
with
skew
quadrupoles
[5];
iii)
fine
coupling
generated
with
skew
quadrupoles
[5];
iii)fine
fine
adjustment
ofofboth
tune
and
chromaticity
allall
adjustment
tune
and
chromaticity
along
the
adjustment
ofboth
both
tune
and
chromaticity
allalong
alongthe
the
PS
cycle.
This
includes
the
fast
change
of
PSPScycle.
sign
cycle.This
Thisincludes
includes the
the fast
fast change
change of
ofsign
signatat
at
transition
crossing
totoavoid
head-tail
instability.
transition
crossing
head-tail
instability.
transition
crossing
toavoid
avoid
head-tail
instability.
FIGURE
3. Vertical
TMC
FIGURE
TMC instability
instability atatat transition
transition for
for
FIGURE 3.
3. Vertical
Vertical TMC
instability
transition
for
high-intensity,
single-bunch
beam
asasobserved
by
high-intensity,
single-bunch
beam
observed
byaaapick-up
pick-up
high-intensity, single-bunch beam as observed by
pick-up
(upper
trace Σ,Z,centre
∆x, lower
(upper
lower∆y,
Ay,hor.
hor.scale
scaleisisis10
10ns/div).
ns/div).
(upper trace
trace Σ, centre
centre Ax,
∆x, lower
∆y,
hor.
scale
10
ns/div).
HIGH-INTENSITY
HIGH-INTENSITY
BEAMS
HIGH-INTENSITYBEAMS
BEAMS
The
The
PSPSroutinely
routinely
produces
two
flavours
ThePS
routinelyproduces
producestwo
two flavours
flavours ofof
of
high-intensity
beam,
namely
singleand
multi-bunch.
high-intensity
high-intensitybeam,
beam,namely
namelysinglesingle-and
andmulti-bunch.
multi-bunch.
FIGURE
FIGURE
Bunchcompression
compressionby
byRF
RFphase
phasejump.
jump.The
The
FIGURE4.4. Bunch
compression
by
RF
phase
jump.
The
beam
beam
distribution
vs.time
timeand
lengthisisisshown
shownon
onthe
the
beamdistribution
distributionvs.
andbunch
bunchlength
length
shown
on
the
left.
left.The
Thesuperposition
thebeam-profiles
beam-profilesatat
different
times
left.
The
superpositionofofthe
atdifferent
differenttimes
times
isisisshown
shownonon
onthe
(hor.scale
scaleisis20
20
ns/div).
shown
theright
right(hor.
20ns/div).
ns/div).
Single-Bunch
Beams
Single-Bunch
Beams
Single-Bunch
Beams
AAAhigh-intensity,
high-intensity,short,
short,single-bunch
single-bunchbeam
beam isisis
high-intensity,
short,
single-bunch
beam
delivered
deliveredtototothe
thenTOF
nTOFfacility.
facility.The
Theexperiments
experiments
delivered
the
nTOF
facility.
The
experiments
require
a a beam
require
a beam
beamofofofthe
thehighest
highestpossible
possibleintensity,
intensity,
require
the
highest
possible
intensity,
together
with
rms
bunch
length
shorter
than
7ns,
ns,toto
to
together
with
rms
bunch
length
σo
shorter
than
77ns,
together
with
rms
bunch
length
shorter
than
b
bσ
b
allow
for
high
precision
time-of-flight
measurements.
allow
for
high
precision
time-of-flight
measurements.
allow
for
high
precision
time-of-flight
measurements.
practice, typical
typical beam
beam parameters
parameters are:
are:
InInIn practice,
practice,
typical
beam
parameters
are:
121212
7×10
p/b
and
σ
about
6
ns
at
extraction
7×10
p/b
and
σ
about
6
ns
at
extraction
NN
b
b
~7xl0
p/b
and
o
about
6ns
at
extraction
b
bN
b
b
(occurring
at2020
GeV/c)
[6].
(occurring
atat20
GeV/c)
[6].
(occurring
GeV/c)
[6].
The
transverse
beam
emittancesdelivered
deliveredby
bythe
the
The
transverse
beam
emittances
The
transverse
beam
emittances
delivered
by
the
PSB
are
quitelarge
largefor
forthese
thesebeams.
beams.Usually,
Usually,atatat
PSB
are
quite
PSB
are
quite
large
for
these
beams.
Usually,
injection,
the
physicaltransverse
transverseemittances
emittancesare
are
injection,
the
2σ
physical
injection,
the
2a2σ
physical
transverse
emittances
are
ε(2o)
=23
23
µm
andεye(2σ)
ε(2o)
=12
12
µm,
slightlybeyond
beyond
x(2σ)
y(2σ)
εx8(2σ)
=
23
µm
and
=
12
µm,
slightly
=
|im
and
=
|im,
slightly
beyond
x
y
the
limit
defined
the
machine
acceptance
60and
and
the
limit
defined
by
the
machine
acceptance
ofofof60
the
limit
defined
byby
the
machine
acceptance
60
and
20
µm.
This
explains
why
beam
losses
cannot
be
2020µm.
|im.This
Thisexplains
explains why
whybeam
beam losses
losses cannot
cannot be
be
reduced
below
the
level
of
10-20
%.
reduced
reducedbelow
belowthe
thelevel
levelofof10-20
10-20%.
%.
The
longitudinal
emittance
cannot
exceed2.5
2.5eVs,
eVs,
The
Thelongitudinal
longitudinalemittance
emittancecannot
cannotexceed
exceed
2.5
eVs,
otherwise
it
would
not
be
possible
to
meet
the
otherwise
otherwise itit would
would not
not bebe possible
possible toto meet
meet the
the
requirement
on
the
final
bunch
length.
Moreover,
its
requirement
requirementononthe
thefinal
finalbunch
bunchlength.
length.Moreover,
Moreover,itsits
lower
limit
is
dictated
by
the
presence
of
a
vertical
lower
lowerlimit
limitisisdictated
dictatedbybythe
thepresence
presenceofofaavertical
vertical
Transverse Mode Coupling (TMC) instability at
Transverse
Transverse Mode
Mode Coupling
Coupling (TMC)
(TMC) instability
instability atat
transition energy [7,8] (see Fig. 3). To cure the
transition
transition energy
energy [7,8]
[7,8] (see
(see Fig.
Fig. 3).
3). To
To cure
cure the
the
instability, εl has to be increased from 1.5 eVs, as
instability,
εl81has
toto bebe increased
from
1.5
eVs,
asas
instability,
has
increased
from
1.5
eVs,
delivered by the PSB, to about 2.3 eVs (see Refs. 7, 8
delivered
bybythe
delivered
thePSB,
PSB,totoabout
about2.3
2.3eVs
eVs(see
(seeRefs.
Refs.7,7,88
for more details), by means of controlled longitudinal
for
more
by
means
of
controlled
longitudinal
forblow-up.
moredetails),
details),
by
means
of
controlled
longitudinal
A non-adiabatic RF gymnastics generates the
blow-up.
AAnon-adiabatic
RF
gymnastics
generates
the
blow-up.
non-adiabatic
RF
gymnastics
generates
the
final short
bunch: the RF
phase
is flipped
by 180º
Q and
final
short
bunch:
the
RF
phase
is
flipped
by
180º
and
final
short
bunch:
the
RF
phase
is
flipped
by
180
and
the bunch placed on the unstable phase. Then, the
the
bunch
unstable
phase.
Then,
the
the
bunch
placed
theoriginal
unstable
phase.
Then,
the
phase
is placed
set
backonon
to the
its
value,
after
sufficient
phase
is
set
back
to
its
original
value,
after
sufficient
phase
is
set
back
to
its
original
value,
after
sufficient
time has elapsed for the bunch to be lengthened. The
time
haselapsed
elapsed
foristhe
the
bunch
tobebe
lengthened.
The
time
has
for
bunch
lengthened.
The
compression
ratio
about
2.5 to
(see
Fig.
4).
compressionratio
ratioisisabout
about2.5
2.5(see
(seeFig.
Fig.4).
4).
compression
Multi-Bunch
Beams
Multi-BunchBeams
Beams
AA
Atypical
typicalhigh-intensity
multi-bunch
beam
isis the
the
typical
high-intensitymulti-bunch
multi-bunch beam
beam is
the
onerequired
requiredby
experiments.
Presently,
the
one
one
required
byneutrino
neutrinoexperiments.
experiments. Presently,
Presently, the
the
13
13
PSisis
iscapable
delivering NNt tt ~ 3.3×10
3.3×10
ppp
in
PS
PS
capableofofdelivering
3.3xl013 ppp
ppp in
in 88
bunches,with
(2σ)
and
similar
to
nTOF
beam
bunches,
(2σ)
x,y
bunches,
with εx,y
eεx?y
(2a)and
and εε81
similarto
tonTOF
nTOFbeam
beam
l l similar
values.For
Forthe
theCNGS
CNGSbeam,
beam,
study
under
way
[9]
values.
isis
values.
For
the
CNGS
beam,aaastudy
study
isunder
underway
way[9]
[9]
13
13
5×10
ppp.
Improvements
aimingatat
atapproaching
approachingNN
aiming
aiming
approaching
Nt tt ~5×10
5xl013ppp.
ppp.Improvements
Improvements
areforeseen
foreseeninin
inthe
thePS
PS both
both
low
and
high
energy
are
are
foreseen
the
PS
both atat
at low
lowand
and high
high energy
energy
(tests
for
doubling
PSB
repetition
rate
are
also
in
(tests
(tests for
for doubling
doubling PSB
PSB repetition
repetition rate
rate are
are also
also in
in
progress
[10]).
progress
[10]).
progress [10]).
ImprovementsAt
AtLow
Low
Energy
Improvements
Improvements
At
LowEnergy
Energy
By
injecting
two
PSB
batches,
similarly
to
what
isis
By
Byinjecting
injectingtwo
twoPSB
PSBbatches,
batches,similarly
similarlyto
towhat
whatis
done
for
the
LHC
beam,
it
is
possible
to
obtain
done
888
done for
for the
the LHC
LHC beam,
beam, itit isis possible
possible toto obtain
obtain
12
12
12 p/b,
bunches
circulating
in
the
PS
with
N
=
6.2×10
b
bunches
circulating
in
the
PS
with
N
=
6.2×10
p/b,
bunches circulating in the PS with Nb b = 6.2x10 p/b,
totalbunch
bunchlength
lengthofof
ofabout
about
190
ns,
(2σ) = 22
µm,
total
total
bunch
length
about190
190ns,
ns,εεexx(2σ)
22µm,
|im,
x(2o)==22
and
ε
(2σ)
=
9
µm.
The
emittance
values
just
fit
the
PS
y
and
andεy8(2σ)
|im.The
Theemittance
emittancevalues
valuesjust
justfitfitthe
thePS
PS
y(2a)==99µm.
acceptance
with
only
few
percent
of
losses.
The
acceptance
acceptance with
with only
only few
few percent
percent ofof losses.
losses. The
The
generation of flat bunches in the PSB [11] would allow
generation
generationofofflat
flatbunches
bunchesininthe
thePSB
PSB[11]
[11]would
wouldallow
allow
to decrease the space charge tune-shift to acceptable
totodecrease
decreasethe
thespace
spacecharge
chargetune-shift
tune-shift toto acceptable
acceptable
values, such as –0.15 and –0.27 in the horizontal and
values,
values,such
suchasas–0.15
-0.15and
and–0.27
-0.27ininthe
thehorizontal
horizontaland
and
vertical plane respectively.
vertical
verticalplane
planerespectively.
respectively.
Improvements At High Energy
Improvements
ImprovementsAt
AtHigh
HighEnergy
Energy
Presently, the so-called Continuous Transfer
Presently,
Continuous
Transfer
Presently,
the
so-called
Continuous
Transfer
(CT)
[12] is the
usedso-called
to extract
the multi-bunch
(CT)
[12]
is
used
to
extract
the
multi-bunch
(CT)
[12]
is
used
to
extract
the
multi-bunch
high-intensity beam. This is a five-turn extraction
high-intensity
beam.
Thisisisissplit
five-turn
extraction
high-intensity
This
aa five-turn
extraction
mode, where beam.
the beam
by means
of an
mode,
where
the
beam
is
split
by
means
an
mode,
where
the
beam
is
split
by
means
ofof are
an
electrostatic septum. Hence, losses (10-20 %)
electrostatic septum.
septum. Hence,
Hence, losses
losses (10-20
(10-20 %)
%) are
are
electrostatic
60
intrinsic
unavoidable. To
To increase
increase the
the overall
overall
intrinsic and
and unavoidable.
intensity
and
minimize
radiation
damage,
a new
new
intrinsic and
To increase
the aoverall
intensity
and unavoidable.
minimize radiation
damage,
approach
has
been
proposed
[13-14].
intensity
and
minimize
radiation
damage,
a
new
approach has been proposed [13-14].
the tests
tests ofofthe
theextraction
extractionbased
basedononadiabatic
adiabatic
toto the
trapping
in
islands
of
transverse
phase
space,
aiming
to
the tests
of the
extractionphase
basedspace,
on adiabatic
trapping
in islands
of transverse
aiming at at
reducing
losses
and
increasing
machine
reliability.
trapping
in
islands
of
transverse
phase
space,
aiming
reducing losses and increasing machine reliability. at
reducing losses and increasing machine reliability.
approach
has
been proposed
[13-14]. to create stable
Using
sextupoles
and octupoles
octupoles
Using sextupoles
and
to create stable
islands,
varying
the
linear
tune, to
possible
Usingand
andlinear
octupoles
create
stable
islands,
andsextupoles
varying the
tune,
itit isis
possible
toto
capture
adiabatically
into the
theisislands
islands
islands, the
and beam
varying
the linear tune,
it
possible
capture
the
beam
adiabatically
into
ofoftoaa
fourth-order
resonance.
Once the
the
beam
split,ofthe
the
capture the beam
adiabatically
intobeam
the islands
a
fourth-order
resonance.
Once
isis split,
extraction
to the
canOnce
take place
place
withfewer
fewer
losses.
fourth-order
resonance.
the beam
is
split,
the
extraction
SPS can
take
with
losses.
extraction
to thethe
SPSresults
can take
place withsimulations.
fewer losses.
Figure
5 reports
results
of numerical
numerical
simulations.
Figure
of
Figure 5 reports the results of numerical simulations.
Fractional
Fractional
tune tune
0.252
Injectors",M.,
CERN-PS-2001-011-DR,
Injectors”,
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neutrino
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3. Andriamonje,
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proton
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proton
4. Benedikt,
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etLHC:
al.,
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design
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forthethe
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and
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Effectsin
inthethe
CERN-PS
beam
for
LHC"
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Effects
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the
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Synchrotrons”,
Single-Bunch
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Initial state: no islands
a
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Capture process
a
0.252
0.250
REFERENCES
REFERENCES
REFERENCES
Benedikt,M.,
M.,et etal.,al.,“Performance
"Performanceof ofthetheLHC
LHC
Pre1.1. Benedikt,
Pre-
b
0.250
0.248
Capture processTransport
within islands
Transport
c
within islands
b
0.248
0.246
Extraction
0.246
0.244
0
5000
0
c
10000
15000
Extraction
Turn number
0.244
5000
10000
15000
20000
20000
Turn number
FIGURE 5.
5. Results
FIGURE
Results of
of numerical
numerical simulations
simulations ofofbeam
beam
FIGURE
5. Results
of numerical
simulations
of beam
splitting
obtained
by
means
of
a
fourth-order
resonance.
splitting
obtained
by
means
of
a
fourth-order
resonance.
splitting obtained by means of a fourth-order resonance.
Preliminary analysis
of
by
Preliminary
analysis
of phase
phase space
space topology
topology by
by
Preliminary
analysis
of
phase
space
topology
means
of
multi-turn
beam
position
measurements
[15]
means
of
multi-turn
beam
position
measurements
[15]
means of multi-turn
beam position
measurementsstable
[15]
confirms
the possibility
confirms
the
possibility of
of generating
generating four
four stable
stable
confirms
of
generating
four
islands
(seethe
Fig.possibility
6).
islands
islands (see
(see Fig.
Fig. 6).
6).
0
25
SO
75
Normalised Phase Plane
-
4
-
2
0
2
-0.4
-0.2
FIGURE 6. Horizontal phase space reconstruction obtained
FIGURE
6. Horizontal
Horizontal
phase
reconstruction
with
multi-turn
measurements
kicked
beam in the obtained
PS.
FIGURE
6.
phaseofspace
space
reconstruction
obtained
with
multi-turn
measurements
of
kicked
with multi-turn measurements of kickedbeam
beamininthe
thePS.
PS.
CONCLUSION
CONCLUSION
CONCLUSION
CERN PS activities related with high-density
CERN
PScontinue,
activities related
with emphasis
high-density
beams
willPS
special
on
CERN
activitieswith
related
with high-density
beams will continue, with special emphasis on
production
the ultimate,
of the emphasis
single-bunch
beams
willof continue,
withandspecial
on
production of the ultimate, and of the single-bunch
pilot LHC beams.
As
far as the
high-intensity
beams
production
of
the
ultimate,
and
of
the
single-bunch
pilot LHC beams. As far as the high-intensity beams
(CNGS)
arebeams.
concerned,
studies
will
be devoted mainly
pilot
LHC
As far
as the
high-intensity
beams
(CNGS)
are concerned,
studies
will
be devoted mainly
to the intensity
increase studies
of the multi-bunch
beam
and
(CNGS)
are
concerned,
will
be
devoted
mainly
to the intensity increase of the multi-bunch beam and
to the intensity increase of the multi-bunch beam and
CERN-PS-2002-018-AE, 2002.
61