ess-bilbao initiative workshop. charge to working group: accelerator components/ beam dynamics
Post on 31-May-2015
1.251 Views
Preview:
DESCRIPTION
TRANSCRIPT
Charge to working group: accelerator components/beam dynamicsF. Gerigk, C. Prior
ESS-B initiative workshop, 16.-18.03.2009
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
Outline
2
goals, expected results,
scope of the session,
accelerator design/beam parameters,
key questions per subject,
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
goals, expected results
3
goal of the workshop:
bring together people working on subjects important to high-power spallation sources,
identify challenges of next generation machines,
propose necessary R&D programs,
identify common areas/interests with other projects.
expected result:
a summary document highlighting the challenges,
addressing future prospects,
define potential collaborative developments programmes,
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk4
This workshop is not a design review of ESS!!
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk5
...instead, this is where we start to develop recommendations for any future high-power
(long-pulse) spallation source
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
scope of the session
6
high-power, highly reliable front-ends,
high-intensity light ion linacs: component design, performance of existing machines, reliability,
synergies with ongoing and planned linac projects,
low-energy superconducting structures (< 100 MeV?),
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk7
beam parameter ⇔ linac designhow the basic target parameters influence the linac design
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
beam parameters ⇔ linac design
8
target/instrument requirements
linac design
beam power ~ 5 MW ?
pulse width ~ ms ?
beam energy 1 GeV (... 3 GeV ?) ?
repetition rate ≤ 20 Hz (15,20,25 ??) ?
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
linac constraints (simplified..)
9
peak power/coupler: Ppeak≤1 MW
average power/coupler: ~50/120 kW
(TTF type 1300 MHz/LHC 400 MHz)
space charge:
max. cavity voltage:Vacc=Ppeak/Ipulse,average
Pav=Ppeak*(tpulse*frep)
beam stability (emittance increase, beam loss, machine
activation)
examples:150 mA: 6.7 MV50 mA: 20 MV
2 ms, 20 Hz: 40 kW2 ms, 40 Hz: 80 kW
high current (150 mA)yields high probability for
loss limited machine performance and/or
need for front-end funnel
cavity gradient (+ n. of cav. families): ≤ 20 - 25 MV/m
frequency/number of cells per cavity
704 MHz: 5/6 cells1300 MHz: 9/10 cells
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
beam parameters ⇔ linac design
10
1 GeV, 16.7 Hz, 2 ms, 5 MW
150 mA, Eacc = 6.7 MV, linac length = l0
first order scaling...
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
beam parameters ⇔ linac design
10
1 GeV, 16.7 Hz, 2 ms, 5 MW
150 mA, Eacc = 6.7 MV, linac length = l0
3 GeV, 16.7 Hz, 2 ms, 5 MW
50 mA, Eacc = 20 MV, linac length = l0
first order scaling...
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
beam parameters ⇔ linac design
10
1 GeV, 16.7 Hz, 2 ms, 5 MW
150 mA, Eacc = 6.7 MV, linac length = l0
3 GeV, 16.7 Hz, 2 ms, 5 MW
50 mA, Eacc = 20 MV, linac length = l0
2.5 GeV, 20 Hz, 2 ms, 5 MW
50 mA, Eacc = 20 MV, linac length = l0*16.7/20=0.83*l0
first order scaling...
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
beam parameters ⇔ linac design
10
1 GeV, 16.7 Hz, 2 ms, 5 MW
150 mA, Eacc = 6.7 MV, linac length = l0
3 GeV, 16.7 Hz, 2 ms, 5 MW
50 mA, Eacc = 20 MV, linac length = l0
2.5 GeV, 20 Hz, 2 ms, 5 MW
50 mA, Eacc = 20 MV, linac length = l0*16.7/20=0.83*l0
2 GeV, 25 Hz, 2 ms, 5 MW
50 mA, Eacc = 20 MV, linac length = l0*16.7/25=0.67*l0
first order scaling...
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk11
target/instrument requirements
linac design
beam power ~ 5 MW fixed
pulse width ~ ms fixed
beam energy 1 GeV (... 3 GeV ?)high/low pulse current, length
constant
repetition rate ≤ 20 Hz (15,20,25 ??)higher rep. rate ⇒shorter linac
beam parameters ⇔ linac design
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
⇒ Questions with high impact on linac design/cost/reliability:
12
1.) linac:how strict is the limit of 1 MW/coupler? how difficult are 2 couplers/cavity?are 20 - 25 MV/m realistic?source/front-end limitations (current/time structure)?
2.) beam dynamics:what are the current limits to avoid a funnel in the front-end?current limits for low-loss operation in the linac?
3.) target:how do different energies (1,2,3 GeV) and rep-rates (16, 20, 25 Hz ..) influence the target design?
4.) instruments:how hard is the limit on the repetition rate (16, 20, 25 Hz ..)?
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
Parameter review of CERN SPL
13
RF frequency & cryogenic temperature
CERN-AB-2008-067
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
SPL (high-power version):
14
HP-SPL (5 GeV)
H- source RFQ chopper DTL CCDTL PIMS
3 MeV 50 MeV 102 MeV
352.2 MHz
β=0.65 β=1.0
732 MeV 5 GeV
704.4 MHz
160 MeV
kinetic energy 5 GeV
beam power 3-8 MW
repetition rate 50 Hz
pulse length up to1.2 ms
average pulse current 0-40 mA
cavity gradient (β=0.65/1.0) 19/25 MV/m
protons p. pulse 1.5 1014
length (SC linac) 472 m
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
RF frequency review: 704 MHz
15
frequency 704 MHz 1408 MHzlength 472 m +12%
Ncavities 246 +15%
Nβ-families 2 3
ε-growth (x/y/z) 5.6/8.2/6.8 6.3/7.8/12.1
long. beam loss none in simulations lossy runs for realistic RF gradient/phase variations
BBU (HOM) IBBU,704 1/(8..128)
trapped modes normal risk 2..4 higher riskRF power density limit (RF
distribution) ok problematic
klystrons comfortable: MBK difficultoverall power consumption
(RF+cryo, nom. SPL) 28 MW up to -30%
power converter more bulky saves tunnel space
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
cryogenic temperature review: 2K
16
@ 704 MHz T [K]eq. capacity @ 4.5 K [kW]
el. power[MW]
HP SPL, 2% beam d.c. (4% cryo d.c.) 2 19.4 4.48
HP SPL, 2% beam d.c. (4% cryo d.c.) 4.5 104 26.0
LP SPL, 0.24% beam d.c. (0.32% cryo d.c.) 2 6.1 1.5
LP SPL, 0.24% beam d.c. (0.32% cryo d.c.) 4.5 11 2.75
not clear that 25 MV/m can be achieved at 4.5 K!
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
questions to the working group:
17
has anyone done a similar analysis?is there experience with high-power RF equipment at high duty cycle (~5%) for high frequencies (≥1200 MHz): klystrons, circulators, RF loads, phase shifters, splitters,...sensitivity to higher order modes for high-current machines (50/150 mA)? Is there any relevant experience?
Dedicated workshop on HOMs in high-power linacs will take place at CERN (~June, exact date to be decided)
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk18
key questions per subject....common to many SC high-power linacs
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
further questions
19
1.) instrumentation:
high power proton machines: how can we do profile measurements during regular operation?
ionisation detector readings disturbed by X-rays from the cavities,
neutron detectors?
halo diagnostics (loss management) 10-5 - 10-6 fractional beam?,
localised beam loss measurements in well shielded low-energy beam (<100 MeV)?,
high-energy emittance measurements?,
beam instrumentation inside accelerating structures?,
beam centre, profile, emittance to <1%?
P. Ostroumov
J. Galambos
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk20
questions II
3.) cryo-modules:how many layers of insulation?
how many cavities per module? length of cryo-modules?
warm or cold focusing magnets?
conversion of electron modules (TTF/XFEL) for protons?
parallel handling of 2K and 4K two phase circuits?
pressure vessel codes conformance issues?
interplay of module and cryo-system design?
Dedicated workshop on segmentation of cryo-modules will be organised by FNAL/CERN (~September, exact date to be decided)
2.) reliability (spare parts):
for which machine elements are spares necessary? (apart from the obvious ones..): source, RFQ, cryo-modules (how many),
P. Pierini
J-L. Biarotte: fault tolerance
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
questions III
21
4.) power converters:
R&D effort to get a reliable, high duty cycle pulsed power supply?
can we use a DC power supply with pulsed mod-Anode power supply for RF test stands? instead of pulsed power supplies (or even for machine operation?), size? operational impact? droop? (can it be compensated by LLRF?)
how much distance can we have between a modulator and the klystrons? 1, 10, 100 m? state of the art in cables? cost comparison to housing the modulators in the tunnel?
R. Cassel
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk22
questions IV5.) low-beta cavities (<200 MeV):
optimum structures (NC or SC) for various beta regions?,
simplification/standardisation of mechanical construction/tuning?,
influence of low-loss beam dynamics on structure design?
6.) medium/high-beta SC cavities:
transition energies NC/spoke/elliptical,
how many cavity families,
realistic gradients for each structure type (and beta),
best recipes for surface treatment,
M. Vretenenar
E. Zaplatin
S. Bousson
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
questions V
23
7.) power and HOM couplers:
peak/average power limits?
adaption/re-design of existing devices for different frequencies?
damping requirements (beam dynamics)?
power and HOM couplers for spoke cavities?
S. Belomestnykh
8.) RF power splitting:
how many cavities per klystron?
fast amplitude/phase shifters (high duty cycle)?
flexibility/reliability compared to single sources?
R. Pasquinelli
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
questions VI
24
A. Letchford9.) Front-ends:
space charge limits?
source, LEBT (space charge compensation), RFQ?
R. Duperrier
10.) Linac modelling:
how close are simulations to reality?
code capabilities?
do we understand LEBT modelling?
J. Stovall
C. Prior
11.) machine activation:
beam loss in high-power machines
M. Seidel
“Accelerator Components”, ESS-B workshop 2009, F. Gerigk
questions VII
25
9.) Collaborations:
Which other projects have similar questions?
A. Mosnier
top related