Status

1
Status plans of the SPL study

• Why upgrade the proton beams at CERN ?
• Approved physics programme
• Potential extensions of the physics programme
• Why a high energy linac ?
• Linac versus RCS
• World-wide context
• How ?
• SPL design
• R. D. topics and collaborations
• Staging
• Roadmap and resources

SPL Superconducting Proton Linac A concept
for improving the performance of the proton beams
at CERN, ultimately based on a high-energy
Superconducting Linear Accelerator
2
The SPL Working Group
REFERENCES
- Conceptual Design of the SPL, a High Power
Superconducting Proton Linac at CERN Ed. M.
Vretenar, CERN 2000-012 - SPL web site
http//cern.web.cern.ch/CERN/Divisions/PS/SPL_SG/
3

• PART 1
• WHY ?

4
Why upgrade the proton beams at CERN ? (1)
Long-term Scientific Programme at CERN (from
CERN/SPC/811)
LHC
SPS Fixed target
PSB PS
5
Why upgrade the proton beams at CERN ? (2)

• Because users will miss protons

PS supercycle for LHC
PS supercycle for CNGS
Remaining PSB PS pulses to be shared between
nTOF, AD, ISOLDE, East Hall, Machine studies
6
Why upgrade the proton beams at CERN ? (3)

• Because higher beam performance (brightness)
  will be first, welcome, and later, necessary to
• Reliably deliver the ultimate beam actually
  foreseen for LHC,
• Reduce the LHC filling time,
• Increase the proton flux onto the CNGS target,
• Prepare for further upgrades of the LHC
  performance beyond the present ultimate.

For protons, brightness can only degrade along
a cascade of accelerators Þ Any improvement has
to begin at the low energy (linac) end
7
Why upgrade the proton beams at CERN ? (4)

• To address new physics programmes
• Neutrino Super-Beam ( conventional but very
  intense neutrino beam)

Accelerator, target and decay channel at CERN
Detector in the Frejus tunnel (400 ktons)
8
Why upgrade the proton beams at CERN ? (5)

• To address new physics programmes
• EURISOL (Next generation of ISOLDE-like source of
  radio-active isotopes)

                                    _ 
         European Isotope Separation On-Line
Radioactive Nuclear Beam Facility
The EURISOL project is one of the 5 Research and
Technical Development (RTD) projects in Nuclear
Physics selected for support by the EU. The
project is aimed at completing a preliminary
design study of the next-generation European ISOL
radioactive nuclear beam (RNB) facility. The
resulting facility is intended to extend and
amplify, beyond 2010, the exciting work presently
being carried out using the first-generation RNB
facilities in various scientific disciplines
including nuclear physics, nuclear astrophysics
and fundamental interactions. Careful design and
developments will be needed to increase the
variety and the number of exotic ions available
per second to be provided for research, beyond
the limits of presently available facilities.
9
Why upgrade the proton beams at CERN ? (6)

• To address new physics programmes
• b beams to Frejus

10
Why upgrade the proton beams at CERN ? (7)

• To address new physics programmes
• Neutrino Factory

1021 y-1
1/g dominates
31020 n/year to each experiment
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Why upgrade the proton beams ?Summary of reasons

• Approved physics experiments
• CERN Neutrinos to Gran Sasso (CNGS) increased
  flux ( 2)
• Anti-proton Decelerator increased flux
• Neutrons Time Of Flight (TOF) experiments
  increased flux
• ISOLDE increased flux, higher duty factor,
  multiple energies
• LHC faster filling time, increased operational
  margin
• Future potential users
• LHC performance upgrade beyond ultimate
• Conventional neutrino beam from the SPL
  super-beam
• Second generation ISOLDE facility (EURISOL
  -like)
• Neutrino source from beta beams
• Neutrino Factory

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Why a high energy linac ? (1)

• 4 MW of beam power at 2-3 GeV are needed
• The energy of the linac injecting into the first
  synchrotron has to be increased (50 MeV today)
• Comparing a Linac fixed energy rings set-up
  with a 2-3 GeV Rapid Cycling Synchrotron (RCS)
• The linac set-up can accommodate more users since
  its beam power can be increased,
• Some users prefer the long beam pulse delivered
  by a linac,
• The RCS construction cost could be smaller, but
  this is moderated by the availability of the LEP
  RF equipment which a linac will re-use
• Linac maintenance is likely to require less
  manpower

13
Why a high energy linac ? (2)LEP RF equipment
A large inventory of LEP RF equipment is
available (SC cavities, cryostats, klystrons,
waveguides, circulators, etc.) which can
drastically reduce the cost of construction
The LEP klystron
Storage of the LEP cavities in the ISR tunnel
14
Why a high energy linac ? (3)World-wide context
High Power Linacs Survey (H,H-,D)
Updated during the 20th ICFA Beam Dynamics
workshop (FNAL, 8-12 April 2002)
Name Ion Pulse length (ms) FRep (Hz) Duty factor () IBunch (mA) IAverage (mA) Energy (GeV) PAverage (MW) Start date
LANSCE H/H- 0.625 100/20 6.2/1.2 16/9.1 1.0/0.1 0.8 0.8/0.08 On
SNS H- 1.0 60 6.0 38 1.4 1.0 1.4 2006
CERN SPL H- 2.8 50 14 22 1.8 2.2 4.0 ?
ESS Short Pulse ESS Long Pulse H- H- or H 1.2 2/2.5 50 16.67 6.0 4.2 114 114/90 3.75 1.33 5 5 2010
FNAL 8 GeV H/H-/e 1.0 10 1.0 25 0.25 8.0 2.0 ?
JKJ 400 MeV JKJ 600 MeV H- 0.5 50/25 25 2.5 1.25 50 0.7 0.35 0.4 0.6 0.28/0.14 0.21 2006 ?
TRASCO H CW 100 30 30 ³1.0 ³30 ?
IFMIF D CW 100 2x125 2x125 0.040 10.0 2010
15

• PART 2
• HOW ?

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SPL Design - Basics

• Basic parameters
• ? Energy gt2 GeV (PS injection, p production)
• ? Max. repetition rate 50 Hz (limit for SC
• cavities)
• ? Beam power 4 MW (limit of target technology)

Design principles ? 352 MHz frequency (LEP) for
all the linac (standard RF, easy long.
matching) ? start room-temperature, go to SC as
soon as possible ? trade-off between current and
pulse length (best compromise SC/RT)
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SPL Design - Parameters
chopping
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SPL Design - Layout
55 cryostats, 33 from LEP, 22 using
components (68 total available)
49 klystrons (44 used in LEP)
Note no more unmodified LEP cavities are used
in the SPL design, for a 87 m shorter linac
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SPL Design Layout on site
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SPL RD guidelines
Identify strategic items (and establish a list of
priorities)
1. Requiring limited resources
2. Essential / critical to the project
3. Where CERN competence is particularly valuable
4. With a maximum of collaboration/exchanges with
other labs
5. Useful for any upgrade of the CERN injectors
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SPL Design RD topics
H- source, 25 mA 14 duty cycle
Cell Coupled Drift Tube Linac
Fast chopper (2 ns transition time)
Beam dynamics studies aiming at minimising losses
(activation!)
new SC cavities b0.52, 0.7, 0.8
RF system pulsing of LEP klystrons
Vibrations of SC cavities analysis, compensation
schemes.
Development of a new Low Level RF (with Linac2)
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RD topics the chopper structure and driver
Chopper Travelling-wave RF deflector (meander
line) at 3 MeV
kicks out the bunches falling between
accumulator buckets (reduce loss at
injection) essential for modern injector linacs !
CERN Chopper structure Alumina substrate,
reduced width (inside quads) Prototypes tested
(attenuation and dispersion) (F. Caspers)

• Driver amplifier
• 2 ns rise-fall time
• (10-90)
• 500 V
• Prototype of HF part
• (M. Paoluzzi)

40 ns
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RD topics the CCDTL
From 40 MeV (up to 120 MeV) the Alvarez can be
replaced by a Cell-Coupled Drift Tube Linac
quadrupole housing
drift tube
1. Quadrupoles outside drift tubes simpler
cooling, access/replacement, alignment 2. Less
expensive structure than DTL 3. Same real estate
shunt impedance 4. Continuous focusing lattice 5.
Stabilised structure (p/2 mode) 6. One
resonator/klystron
coupling cell
4 klystrons
6 klystrons
5 klystrons
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RD collaborations the DTL test stand (with IPHI)
Measurements (ISN Grenoble)
New test stand in the PS South Hall for 352 MHz
linac structures 50 kW CW, 100 kW pulse (just
outside MCR)
DTL model (CEA-Saclay)
Waveguide (ex LEP)
CERN 50 kW amplifier (ex SPS-LEP)
2002 testing the IPHI DTL model (3 drift
tubes) 2003 testing the CERN CCDTL model
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RD topics low b SC cavities

• ? CERN technique of Nb/Cu sputtering
• excellent thermal and mechanical stability
• (important for pulsed systems)
• lower material cost, large apertures, released
• tolerances, 4.5 ?K operation with Q 109

? Bulk Nb or mixed technique for b0.52
(one 100 kW tetrode per cavity)
(E. Chiaveri, R. Losito)
The b0.7 4-cell prototype
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RD topics - vibrations
possible chaotic effects (J. Tückmantel)
Effect on the beam
Effect on field regulation

• vector sum feedback can compensate only
  for vibration amplitudes below 40 Hz
• possible remedies piezos and/or high power
• phase and amplitude modulators
• (prototype ordered - H. Frischholz)

27
RD topics pulsing of LEP klystrons
Mod anode driver
14/05/2001 - H. Frischholz

• LEP power supplies and klystrons are capable
  to operate in pulsed mode after minor
  modifications
• up to 12 klystrons can be connected to one
  LEP power supply

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RD topics loss management
For hands-on maintenance, the generally accepted
figure is a particle loss lt 1 W/m
For the SPL, 10 nA/m (10-6/m) _at_ 100 MeV,
0.5 nA/m (10-7/m) _at_ 2 GeV
Present Linac2 loss level (transfer line) ?
25W/80m 0.3 W/m (but hot spots
at gt 1 W/m !)

• Mechanism of beam loss in the SPL
• H- stripping ? lt 0.01 W/m in quads for an
  off-axis beam
• Residual gas ? lt 0.03 W/m _at_ 10-8 mbar, 2 GeV (but
  0.25 W/m _at_ 10-7)
• Halo scraping ? more delicate, requires
• ? large apertures (SC is good!)
• ? careful beam dynamics design

29
RD topics beam dynamics
? Control rms emittance growth and loss from the
outer halo by avoiding parametric
resonances
? Selection of the working point (phase
advances) on the Hofmanns chart
Careful matching (50Mpart simulations with
IMPACT at NERSC, Berkeley)
(F. Gerigk)
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RD topics after the linac
Transfer lines, collimation ( scrape away halo
particles before the accumulator), etc.
Accumulator/Collector scheme (PDAC study group)
for NuFact
Two Rings in the ISR Tunnel Accumulator 3.3 ms
burst of 144 bunches at 44 MHz Compressor Bunch
length reduced to 3 ns
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Staging 1 a common low-energy test stand with
IPHI
IPHIInjecteur de Protons Haute Intensité
(CEAIN2P3) a 5 MeV CW RFQ _at_ 352 MHz is in
construction and a test stand (2 LEP klystrons)
in preparation at CEA-Saclay.
Agreement reached in April
? IPHI RFQ split at 3 MeV to accomodate the
CERN line
? CERN will assemble a chopper line (choppers,
quads, bunchers)
? Common test stand at CEA Saclay
More details CERN/PS 2002-012 (RF) SUMMARY OF
MINI-WORKSHOP ON SPL AND IPHI R. Garoby
? Further tests (2006) at CERN with an H- source
32
Staging 2 a 120 MeV linac in the PS South Hall
Any upgrade of the CERN injectors to higher
brightness requires a higher energy linac
Profiting of the SPL design, we have a unique
chance to build a new, low-cost and
high- performance linac by using the RT (120 MeV)
part of the SPL to inject H- into the PSB.
Parameters are relaxed, there is enough space
for a linac in the PS South Hall, the RF comes
for free.
33
Staging the 120 MeV linac
to inflector PSB
72 m
34
Staging the 120 MeV linac
35
A new 120 MeV linac at CERN (Linac 4)

• 1. Cost-effective construction
• (the RF is available, including waveguides and
  power supplies, the building is there as well as
  cooling and electricity,)
• Advantages for the LHC beam
• (shorter filling time, more margin for the
  injectors,
• opens the way for an LHC upgrade)
• Many advantages for the users of secondary beams
• (factor 1.8 in flux for CNGS, factor 2 for
  ISOLDE,
• improvements for AD and n-TOF).
• A more modern and easy-to-run injector replacing
• the aging Linac2

36

• PART 3
• ROADMAP
• RESOURCES

37
Roadmap (1)CERN context

• R D on accelerators at CERN - Medium Term Plan
  (SPC/811)

The RD budget for future detectors and
accelerators foreseen in the 2002-2005 MTP and
for the subsequent years to 2010 is reduced in
total by 54.2 MCHF making thus available 26 MCHF
for the completion of the upgrade of the
injectors. The materials budget for RD during
the period 2003-2006 will therefore be limited to
around 3.8 MCHF per year. For the time being,
similar figures are also foreseen, for the years
2007-2010. Direct manpower involved in
accelerator RD is kept over the next 8 years at
about 30 CERN staff and 5 fellows and associates,
full time equivalent per year. It should be
stressed that the above is a minimal programme of
Accelerator RD especially for an accelerator
laboratory of the importance of CERN. Its
narrowness and limitations can only be justified
by the present severe budgetary problems facing
CERN. Efforts will be made to enhance the
synergies in accelerator RD with other
Laboratories by enlarging the scope of ongoing
collaborations and by setting up new ones. In the
years 2002-2004 about 90 of the accelerator RD
resources will go to the construction of the CTF3
facility for CLIC... RD work on components for
the front-end of a Superconducting Proton Linac
(SPL) will continue with limited funds until the
first phase of CTF3 is completed and the testing
of high-gradient accelerating structures is well
advanced. From then on, the sharing of resources
between CLIC and SPL work might evolve as a
function of the results technically achieved and
of the contribution of the collaborations with
other Laboratories. The work on the SPL front-end
is carried out within the framework of
collaboration for powerful H -- sources among
seven European laboratories and with IN2P3/CEA
for a Radio Frequency Quadrupole (RFQ) device
38
Roadmap (2)until 2006

• 5 MeV H- injector (summary of collaboration
  meetings in April 2002)

• Tests at Saclay
• Construction installation of RFQ1
  (3MeV) mid-2004
• CW diagnostic line (3 MeV) beam stopper
• Characterisation in CW up to 100 mA end 2004
• Installation of chopping line RFQ2
  (?) mid-2005
• CW diagnostic line (5 MeV) with
• time resolved instrumentation
• Characterisation at 5 MeV pulsed CW end 2005
• Installation at CERN (without H source) 2006

Resources Need to provide the foreseen CERN
contribution (chopper line and instrumentation), d
evelop an H- source and prepare the
infrastructure for installation. Comment
feasible with the manpower authorised in 2002
500 kCHF/year
39
Roadmap (3) until 2010 ?

• 120 MeV H- linac in the PS South Hall replacing
  LINAC 2 (50 MeV H)
• Goal increase beam intensity for CNGS and
  improve characteristics of all proton beams (LHC,
  ISOLDE)
• Under study detailed design report with cost
  estimate in October 2002

• On-going activities
• Tests at CERN of DTL prototypes (collaboration
  with CEA IN2P3)
• Development of CCDTL structures
• Development of new low level RF
• Study of charge exchange injection in the PSB

Resources Requires an order of magnitude
increase w.r.t. the effort invested in the 5 MeV
injector Comment Active search for external
resources (E.U. etc.). Nothing will be possible
without a clear decision by the CERN management,
linked to the commitment to an adequate support.
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Roadmap (4) until 201x !

• Full size SPL
• Necessary condition approval of (at least) one
  new physics programme (Neutrino super-beam ?
  EURISOL ?)
• Design is not frozen ! (beam energy, type of SC
  cavities)

• On-going activities
• Studies and developments for the 120 MeV injector
• Characterisation of 352 MHz low b SC cavities in
  pulsed mode
• Development of high power amplitude phase
  modulator
• Beam dynamics optimisation

Resources Large size project when combined with
the realisation of high power target area(s) and
new experimental facilities Comment Will need
major contributions in know-how and in-kind from
other laboratories. A clear possibility of
development of CERN after the completion of the
LHC construction
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Roadmap (5)

• The SPL study is alive and supported, although
  with limited resources, and progress is made
• design is improving,
• RD is going on,
• collaborations are active and more is encouraged
  !
• A staged approach is proposed to
• bring immediate benefits to the approved physics
  programme
• help preserve and gradually strengthen a
  competent team
• accelerate the realization of the complete SPL
• Continuation after 2002 depends upon CERN
  management decisions to solve the LHC crisis

42
CONCLUSION

• High intensity protons beams will remain a strong
  asset of CERN beyond 2010. Improving their
  performance is a logical and necessary path for
  the approved physics programme (especially LHC).
• Proposals for new major experimental facilities
  are being prepared (UNO, neutrino super-beams,
  EURISOL, ), for which the CERN site is perfectly
  suitable.
• ß
• A new high performance proton injector like the
  SPL would be a key component to satisfy both
  needs
• Such a project is ideally suited to bridge the
  gap between the end of payment of the LHC
  construction and a future project for high energy
  physics (VLHC ? Linear Collider ? Neutrino
  Factory ? )