empfehlung einer strategieschoning/... · a (second) laser or a particle beam creates strong...
TRANSCRIPT
A.Schöning 1 Accelerator Physics WS 2015/16
Accelerator Physics
Lecture 12
New Technologies Superconducting RF CLIC Technology Plasma Wakefield Accelerators
A.Schöning 2 Accelerator Physics WS 2015/16
Electron-Positron High Energy Collider
LEP: P ~ 100 MW s = 200GeV
LEPX: P ~ 63 GW s = 1000GeV
~63 nuclear plants!!!
International Linear Collider (successor of the TESLA project)
A.Schöning 3 Accelerator Physics WS 2015/16
from E.ElsenRF-Acceleration Concepts
● Resonator required for➔ longitudinal component E
z
➔ adjustment of phase velocity
Two concepts● wakefields
➔ bunch acquires energy whilewave amplitude attenuates
● Standing wave➔ bunch is accelerated by
mean field gradient;field amplitude is hardly affected
E z=E0 cos(ϕ)
E z=E0sin (ω t+ϕ)sin (k z )
A.Schöning 4 Accelerator Physics WS 2015/16
from E.ElsenRF-Generation Concepts
● Klystron➔ velocity and densitiy modulation of electrons generates RF-field➔ electrical field is coupled out
● Wakefied➔ field of compact moving electron bunches generate RF-field in cavitites which are coupled out
A.Schöning 5 Accelerator Physics WS 2015/16
Cavity Basics
∣Z−1∣=∣1
1iωC
+iω L+R∣=ω/L
((ω2−ω0
2)2+ω
2Γ2)1/2
02=
1LC
= = R / L
with series resistor
C L
R
Quality factor:
Q0 =0
=1R LC Ohmic resistor determines quality factor!
104 – 105 normal conducting> 109 superconducting
High frequency oscillator:
cavity circuit
resoncance frequency: bandwidth:
A.Schöning 6 Accelerator Physics WS 2015/16
Superconducting Cavity ILC (TESLA)
f = 1.3 GHz
Niobium
Advantage SC-RF:no electrical resistance!no power losses!
A.Schöning 7 Accelerator Physics WS 2015/16
Superconductor
Meißner-Ochsenfeld Effect
Limitation:
critical magnetic field Hc
H c T ≈H c 01−T2/T c
2
need low temperatures!
Superconductor of first kind
A.Schöning 8 Accelerator Physics WS 2015/16
TESLA Cavity
TESLA TDR
A superconductor in a HF field has a surface resistance RS
B fieldHF field
superconducting
penetration depth(London parameter)
~100 mT~30 MV/m
Superheating: for a short time (HF) magnetic field may exceed critical temperature!
Rs surface resistance
A.Schöning 9 Accelerator Physics WS 2015/16
Superconducting Cavity
Technical problems● thermal instabilities● field emissions
caused by● weld splatters● cracks ● dust
Therefore very clean surface required electro-polishing
strong em. field → heating
maximum acceleration field 35-40 MV/m
A.Schöning 10 Accelerator Physics WS 2015/16
FabricationMaterial niobium Tc=9.2 K
single-crystal (no welding)
small impurities!
careful processing:
high power
water pressure rinsing
heating
chemical polishing
A.Schöning 11 Accelerator Physics WS 2015/16
Yield of CavitiesILC goal: 31.5 MV/m (average)
Yield
A.Schöning 12 Accelerator Physics WS 2015/16
Future Ideas
H0 = 324mTHi = 150mT
d
figures from Elmar Vogel (DESY)
Coating of surface coating reduces magnetic fieldin superconducter and surface resistance (A. Gurevich)
B0
thin layer
A.Schöning 13 Accelerator Physics WS 2015/16
Superconducting MaterialsTask: Find superconductor with high H
C
Problem: Most “high temperature” superconductors are of second kind(incomplete Meißner effect → flux tubes)
flux tubes
HF: walking flux tubes absorb energy!
need SC of 1st kind!
A.Schöning 14 Accelerator Physics WS 2015/16
CLIC
The wakefield accelerator
the bigger the boat → the faster runner
A.Schöning 15 Accelerator Physics WS 2015/16
CLIC from E.ElsenThe CLIC Concept
● high gradient > 100 MV/m➔ compact collider;
total length < 50 km for 3 TeV➔ acceleration in normal
conducting elements @ 12GHz
● Acceleration field generated by parallel high intensity beam
➔ field generated only during acceleration➔ efficient generation of high intensity beam
A.Schöning 16 Accelerator Physics WS 2015/16
CLIC from E.Elsen
A.Schöning 17 Accelerator Physics WS 2015/16
CLIC
from E.Elsen
A.Schöning 18 Accelerator Physics WS 2015/16
Plasma Wakefield Accelerators
A revolutionary technology...
A.Schöning 19 Accelerator Physics WS 2015/16
Plasma Wakefield Accelerators
Driving Beams:● Laser● electron beam● proton beam
E.g.: Proton Driven Plasma Wakefield Accerator:
Use 7 TeV LHC proton beam to transfer energy to
an electron beam of 7 TeV or even higher, fantastic!
F.S.Tsung et. al.
A.Schöning 20 Accelerator Physics WS 2015/16
Acceleration in Plasma
Principle: Plasma is created either by using strong
Lasers or by heating
A (second) laser or a particle beam creates strong electric fields which lead to charge density fluctutations in the plasma
The mobility of ions is given by its mass → electrons move
Charge density fluctutation create strong fields which can be used for acceleration
E field = c me0 p = c n p e
2
0me
electrical field: Plasma frequency:
density fluctutation np = plasma density
F.S.Tsung et. al.
A.Schöning 21 Accelerator Physics WS 2015/16
Plasma Wakefield by Electron Beam
Sketch:
A.Schöning 22 Accelerator Physics WS 2015/16
Proton Driven Plasma Wakefield
electrical field density fluctutation
Simulation (A.Caldwell et. al.):
witness bunch!
long. E-field
2 GeV/m !!!!
A.Schöning 23 Accelerator Physics WS 2015/16
SLAC Result with Electron Beam:
driving beam
accelerated electrons
energy more than doubledin plasma !
A.Schöning 24 Accelerator Physics WS 2015/16
Simulation of 1 TeV Proton Beam
Could be experimentally studied at SPS (E=450 GeV)
protons electrons
However, proton bunches are usuall long ~ 10cm
(A.Caldwell et. al.)
A.Schöning 25 Accelerator Physics WS 2015/16
Microbunching and Self Modulationof Proton Beams
red/blue electrical field black plasma density
(N.Kumar et. al.)
plasma is also modulated using long proton bunches!
Self Modulation
A.Schöning 26 Accelerator Physics WS 2015/16
The Future: Proton Driven Plasma Accelerator at LHC?
A.Caldwell et al. Nature (2009)
1km linear TeV accelerators with large acceleration gradients are possible, in principle!
A.Schöning 27 Accelerator Physics WS 2015/16
AWAKE Collaboration @ CERN
A.Schöning 28 Accelerator Physics WS 2015/16