Transcript Slides - Agenda INFN

Testing Advanced Cooling
Techniques
Vladimir N. Litvinenko
for Coherent electron Cooling team
C-AD, Brookhaven National Laboratory, Upton, NY, USA
Stony Brook University, Stony Brook, NY, USA, AES, Medfrord, NY, USA
SLAC, Palo Alto, USA, Niowave Inc., Lansing, MI, USA, Tech X, Boulder, CO, USA
Budker Institute of Nuclear Physics, Novosibirsk, Russia
STFC, Daresbury Lab, Daresbury, Warrington, Cheshire, UK
Supported by BNL (LDRDs & PD), C-AD AR&DD, and NP DoE office Accelerator R&D grant
eRHIC:
Highly advanced and energy electron-ion collider
eRHIC peak luminosity
arXiv:1409.1633
eRHIC hadron beam is 1,000 x brighter than
current RHIC beams
Energy, GeV
CM energy, GeV
Bunch frequency, MHz
Bunch intensity (nucleons), 1011
Bunch charge, nC
Beam current, mA
Hadron rms normalized
emittance, 10-6 m
Electron rms normalized
emittance, 10-6 m
b*, cm (both planes)
Hadron beam-beam parameter
Electron beam disruption
Space charge parameter
rms bunch length, cm
Polarization, %
33
-2 -1
Peak luminosity, 10 cm s
2
He3
79
Au197
e
p
15.9
250
126
9.4
3.0
48
415
167
103
9.4
3.0
32
275
100
80
9.4
3.0
19.6
165
0.2
0.2
0.2
23
35
58
5
0.004
36
0.08
5
0.003
16
0.08
5
0.008
6
0.08
70
4.1
70
2.8
none
1.7
9.4
0.07
1.1
10
5
0.4
80
5
5
Very strong cooling is required
5
Requirement vs. current cooling
techniques
IBS growth time for eRHIC beam is about 20 seconds (for 250 GeV
protons) and have to be contra-acted by cooling
RHIC’s stochastic cooling can cool 109 ions in 5 nsec bucket with cooling
time ~ 1 hour. It is equivalent to cooling time for eRHIC 0.3 nsec bunches:
– Heavy ions > 10 hours
– Protons > 100 hours
Our best design for electron cooling promised to cool ion beam at 100 GeV
with cooling time of one hour. Extending this $150M facility to cool 250
GeV protons will provide cooling time of bout 30 hours. It would be better
than stochastic cooling, but definitely insufficient for eRHIC
We need a better cooling mechanism.
Coherent Electron Cooling Schemes
E < Eh
Classic – FEL amplifier (2006, PRL VL & YD)
Eh
E < Eh
Hadrons
Modulator
Dispersion section
( for hadrons)
Eh
Kicker
E > Eh
E > Eh

High gain FEL (for electrons)
Electrons
Blended – laser amplifier (2007, VL)
E < Eh
Hadrons
Dispersion section
( for hadrons)
Modulator
Eh
Kicker
E > Eh
Laser Amplifier
R56
Radiator
Electrons
Energy
modulator
Enhanced bunching: single stage - VL, FEL 2007
Micro-bunching: MB Amplifier, Single & Multi-stage, D. Ratner, PRL, 2013
Hadrons
Dispersion section
( for hadrons)
Modulator I
Eh
Micro-bunching Amplifier
R56
Electrons
Modulator 2
-R56/4
Kicker
E > Eh
-R56/4
-R56/4
Modulator 5
5
“Classical: Coherent electron Cooling scheme
Dispersion
At a half of plasma oscillation
qlFEL »
lFEL
ò r(z) cos( k z)dz
cDt = -Dzh ×
FEL
0
rk = kq(j1 ); n k =
Hadrons
rk
2pbe^
g -g o
L
; D free = 2 ; Dchicane = lchicane ×q 2 .......
go
g
E < Eh
Dispersion section
( for hadrons)
Modulator
l1
Eh
E > Eh
Kicker
High gain FEL (for electrons)
l2
Electrons
λFEL
Debye radii
2 RDt
vh
2 RD//
RD //,lab
RD^ >> RD //
cgsqe
RD^ =
wp
cs
= 2 g << lFEL
g wp
Amplifier of the e-beam modulation in an
FEL with gain GFEL~102
A^ =
E > E0
Ez
λFEL
kFEL = 2p / lFEL ; kcm = kFEL /2g o
-q /Ze
(
)
l fel = lw 1+ aw2 /2g o2
wpt
wpt
q = -Ze × (1- cosj1 )
j1 = w p l1 /cg
q peak = -2Ze
E0
2pb ^en / g o
w p = 4 pne e 2 / g ome
Density
λFEL
E < E0
aw = eAw / mc
2
LG = LGo (1+ L)
namp = Go × nk cos(kcm z)
GFEL = e LFEL / LG
Eo = 2Gog o
e
be^n
X = q/ e @ Z(1- cosj1) ~ Z
6
Coherent Electron Cooling Schemes
Enhanced bunching: single stage - VL, FEL 2007
Micro-bunching: Multi-stage 2013, D. Ratner,
Hadrons
Modulator I
Dispersion section
( for hadrons)
Eh
E > Eh
Bunching
l1
R56
Electrons
Enhanced e-cooling
© VL, Gang Wang, 2013
Kicker
l2
CeC limits
Each charged particle causes generation of an electric field wave-packet
proportional to its charge and synchronized with its initial position in the bunch
æ
Etotal (z ) = E o × Imçç X × å K (z - z i )e ik(z -z i ) è i,hadrons
åK (z - z )e
ik (z -z j )
j
j,electrons
ö
÷÷
ø
Eo = 2Go × g o ×
e
be^n
X = q/ e @ Z(1- cosj1) ~ Z
Evolution of the RMS value resembles stochastic cooling!
Best cooling rate achievable is ~ 1/Neff, Neff is effective
number of hadrons in coherent sample (Λk=Ncλ)
L k = òò K ( z-z ) dz
2
d 2 ¢ = -2x d 2 + Dcec
x = -g d i Im ( K ( Dz i ) eikDz
i
)
Lk
N
+ 2e
4ps z,h X
Lk
4ps z,e
/ d2 ;
Z 2 rp ì
l2 ü
Dcec = g N eff / 2; g = Go
í2 f (j 2 ) (1- cosj1 ) ×ý ,
A e ^n î
b þ
2
N eff @ N h
Λk ~ 38 λfel
xCeC (max) µ
1
N eff
t CeC µ
1
~ 250 sec
f × N eff
eRHIC @ 250 GeV -> FEL wavelength 0.5 um, Λk ~ 20 um, Neff~3x107 : it is critical to see if this can be achieved
e ¢ / e = -2g + g2 ® g ~ 1
8
Saturation
9
CeC Proof-of-Principle Experiment
Coherent electron Cooling PoP
Our PoP is based on an economic version of CeC:
it limits strength of the wiggler aw to about 0.5
but it is very cost effective
Param.’s from 40 GeV proof-of-principle exp. at BNL
Bunching
computed from
charge density
perturbation &
entered into
GENESIS FEL
simulation.
VORPAL 3D δf PIC computation of
e- density perturbation near Au+79
ion (green) vs. idealized theory
(blue). On Cray XE6 cluster at
NERSC.
GENESIS output
converted into
VORPAL-compatible
input.
GENESIS parallel computation
of electron beam bunching in
free electron laser (FEL)
shows amplification of
modulator signal.
VORPAL prediction of the
coherent kicker electric field
E k due to e-density
perturbation from modulator,
amplified in the FEL.
Simulations by Tech-X
11
Phase 1 – Beamline installation and 112 MHz Cavity Testing
Coherent electron Cooling PoP
First beam from 112 MHz gun – June 2015
1.6-1.7 MeV (kinetic energy) in CW mode
Laser-generated CW e-Beam with 3 nC @ 5 kHz
20 MV/m at photocathode
It turned out to be a record performance of
any CW photo-injector
CeC PoP 3D rendering
Beam Line
in RHIC IP
Utility Building
Water/Cryogenic
s
Service
Building
Diagnostics
Laser Room
(New)
Service Building
Vacuum
Coherent electron Cooling PoP
PS Building
RF and Magnets
Beamline Components
Coherent electron Cooling PoP
Phase 3 - 704 MHz 5 Cell Cavity From Niowave
Delivery from Niowave – July 15, 2015
Coax in house being installed
FPC welding at AES is finished
704 MHz 5 Cell SRF linac
(cryomodule)
assembled at NioWave Inc
Cliff Brutus welcomes it at IP2
Coherent electron Cooling PoP
Three Helical PM Wigglers at BNL from BINP (Novosibirsk). BINP
team visited in July 2015
Left to right: Domenick Milidantry (SMD), Pavel Vobly (BINP), Ray
Ceruti (SMD), Igor Ilin, Victor and Sergey Shadrin, Vitalii Zuev (all BINP)
and Igor Pinayev (C-AD) near the first assembled helical wiggler
We are on the move with CeC PoP
Schedule
Assembling and tuning helical wigglers
Install 704 MHz in RHIC tunnel
Install helical wigglers in RHIC tunnel
CW laser is commissioned
Beam diagnostics is intalled
Optical diagnostics is installed
Complete CeC beam-line
Commissioning
SRF cavities cold
Complete cavity conditioning
Generating first beam
Measuring beam parameters
Propagate beam to the beam dump
Test co-propagation with ion beam
Demonstrate FEL amplification
First cooling attempt
V 1/3
x
x
x
X
Milestones
x
X
X
X
x
X
X
X
15-Aug-15
15-Nov-15
01-Dec-15
01-Dec-15
15-Dec-15
15-Dec-15
15-Dec-15
15-Feb-16
15-Mar-16
01-Apr-16
15-Apr-16
01-May-16
15-May-16
01-Jun-16
01-Jul-16
Summary
•
Coherent electron cooling promises to boost brightness
of hadron beams by orders of magnitude
•
Progress continues on component installation and
commissioning of coherent electron cooling experiment
•
112 MHz SRF CW gun generated electron beam
•
Installing the rest of equipment in 2015
•
“Classical” CeC test in 2016/2017
•
Micro-bunching amplification in CeC - 2017
Coherent electron Cooling PoP
Back-up slides
Detecting CeC action
Electron bunch – 10 psec
Ion bunch – 2 nsec
r.m.s. length of the cooled part 80-120 ps. The
cooling effects can 2 GHz (or more) bandwidth
using spectrum analyzer or digital scope
Well above noise floor
Simulated Au ion beam
profile evolution with
CeC PoP parameters
Cooling full bunch
Self-consistent simulations
Preliminary, © G.Wang
FEL saturation
Bunching amplitude and phase (CeC PoP)
© Y. Jing
1
4
3
Avg shot noise
Avg Green function
2
0.001
0.0001
1e-05
1e-06
Average bunching (short noise)
0
Bunching Phase
CeC FEL end
0.01
2.5
2
-2
1.5
-4
1
-6
0.5
-8
Peak-value of the averaged
Green function
1e-07
-10
0
2
4
6
8
10
12
14
16
0
0
Longitudinal position [m]
RMS Bunching Phase
0.1
2
4
6
8
10
12
14
16
Longitudinal position [m]
Signal grows exponentially until ~ 9 m with gain at 409 and it continues to
grow and saturates with gain of 777 @ 11.5 m.
g max ~ 144 
I p [ A]  o [ m]
Mc
 858
10% difference between theoretical
estimation and simulation
Main Beam Parameters for CeC Experiment
Parameter
Value
Species in RHIC
Relativistic factor
Number of particles in bucket
Electron energy
Au+79 ions, 40 GeV/u
42.96
109
21.95 MeV
Charge per e-bunch
Rep-rate
Average e-beam current
0.5-5 nC
78.17 kHz
0.39 mA
Electron beam power
8.6 kW
Electron Beam and FEL Parameters
for CeC PoP experiment
Electron Beam
RMS Energy Spread
Normalized Emittance
Peak Current
≤ 1×10-3
≤ 5 μm.rad
60-100 A
FEL
Wiggler Length
Wiggler Period
3×2.5 m
40 mm
Wiggler Strength, aw
FEL Wavelength
0.5 +0.05/-0.1
13.6 μm
Phase 3: Full Energy Beam Line Installation - 2015
•
•
•
•
•
Install 704 MHz Systems and supporting cryogenic system
Install Wiggler Magnets
Install RHIC beam line components: dipoles, quads, correctors, vacuum
Install beam diagnostics Modify and install RHIC DX-DO chamber for FEL
light diagnostics
Move CeC beam dump line to final location