The TESLA Project
Ties Behnke, DESY
TESLA: The machine
" status of cavity development
" RF system
" FEL at TESLA
" accelerator layout
A Detector for particle physics
at TESLA
American Linear Collider Workshop, Baltimore, March 2001
Ties Behnke: The TESLA project
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TESLA
TESLA
The TESLA Collaboration
INFN Legnaro
a machine concept: superconducting
acceleration modules
a collaboration:
build and operate a test accelerator TTF
a proposal to build such a machine
INR Troitsk
MEPhI Moscow
Uni Hamburg
Uni Rostok
BESSY Berlin
American Linear Collider Workshop, Baltimore, March 2001
Yerevan Physics Institut
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TESLA Basic Concept
superconducting solid Nb cavities
E(acc) ~ 25 MV/m, T=2K
Long RF pulses ( ~ 1 ms)
low RF peak power (200 kW/m)
long bunch train with large interbunch
spacing
Low RF frequency (1.3 GHz)
small wakefields
The TESLA acceleration structures:
Overall design compatible with
E(cms) = 91 .... 800 GeV
baseline design and
parameters for 500 GeV
American Linear Collider Workshop, Baltimore, March 2001
module
geometry
module length V(acc)
Fill factor
RF/module
219
9−cell structure
1.04
23.40
78.00%
4x7
superstructure
3.23
22.00
89.00%
675
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TESLA Parameters
TESLA 500 GeV parameters
American Linear Collider Workshop, Baltimore, March 2001
TESLA 800 GeV parameters
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TESLA Bunch Structure
Main characteristics:
long bunch trains, even longer times between bunch trains
500 GeV
5 Hz x 2820 x 2.0 1010
800 GeV
3 Hz x 4568 x 1.4 1010
possibility of orbit corrections within
single bunch train
(fast feedback system)
Head on collisions are possible
Bunch collisions are well separated
in detector
American Linear Collider Workshop, Baltimore, March 2001
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Status of Cavities Development
TESLA Test Facility (TTF) Goals:
Phase I:
development of acceleration modules
proof of principle of operation of SC linac
at high (> 22.5 GeV) gradient
proof of principle for SASE FEL in the VUV (60 nm)
cavity performance
per production series
Tesla
500
American Linear Collider Workshop, Baltimore, March 2001
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American Linear Collider Workshop, Baltimore, March 2001
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RF Power: Klystrons
TH 1801 multi beam Klystron
High power (10 MW peak)
Low voltage (117 kV)
High efficiency (65 %)
Long pulse (1.5 ms)
System has been fabricated in industry
Is now being used at the TTF LINAC
American Linear Collider Workshop, Baltimore, March 2001
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Lorentz Force Deformation
Problem: Cavity deform under the Lorentz force at high gradient
Cavity changes its shape
cavity is detuned
first successful test on cavity C45 at 20 MV/m
solution:
active compensation
using piezo−crystal
l = 39mm
V(max)= 150 V
f(max) = 500 Hz
piezo actuator
American Linear Collider Workshop, Baltimore, March 2001
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The Free Electron Laser at TTF
TTF LINAC is used to drive a SASE FEL
Goal I: Proof of Principle for VUV FEL
Goal II: Operation of user facility after 2003
American Linear Collider Workshop, Baltimore, March 2001
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The TTF FEL
February 2000: observe first lasing at <100 nm
Since then: systematic studies
very reliable and reproducible behaviour
continuous reduction of the frequency
Main radiation characteristics have been found
CCD image of the FEL beam:
American Linear Collider Workshop, Baltimore, March 2001
Signal development
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The TTF FEL
Since observation of first lasing:
continuous further development of the system towards:
FEL operation: brilliance vs energy
Smaller wavelength
better reproducibility
higher brilliance
Development of X−ray energy
American Linear Collider Workshop, Baltimore, March 2001
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Overall TESLA Layout
TESLA tunnel: diameter 5.50 m
Overall collider layout:
DESY
American Linear Collider Workshop, Baltimore, March 2001
Westerhorn
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Collider Layout: Injector
TESLA injector complex:
Laser driven electron guns
Three separate guns for
Unpolarised
Polarised
FEL beam
Electron polarisation is
part of the baseline program
American Linear Collider Workshop, Baltimore, March 2001
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Collider Layout: Positron Source
Positron source: use incoming electron beam as a source of photons
produce positrons
Small degradation of quality of beam is acceptable
Allows very high positron currents
Possibility of positron polarisation
SLC
TESLA
No of positron per pulse
4.00E+010
5.60E+013
No of bunches per pulse
1
2820
Pulse duration
3 ps
0.95 ms
Bunch spacing
8.3 ms
337 ns
Repetition frequency
120 Hz
5 Hz
American Linear Collider Workshop, Baltimore, March 2001
Expected positron polarisation:
between 45 and 60% at (nearly)
full intensity
Need to build a helical undulator
(technologically challenging)
Positron Polarisation is not part of
the baseline design
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The Interaction Region
Conceptual layout of the interaction region(s):
2. IR not part of baseline design
IR for gamma gamma
electron gamma
electron electron
electron positron
34 mrad crossing angle
IR for primary electron positron
program (or electron electron)
no crossing angle
American Linear Collider Workshop, Baltimore, March 2001
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Fast Feedback at the IP
Long bunch trains, long times between bunches:
Feedback system within bunch train possible to stabilise the luminosity
Act on angle
Act on offset
After about 90 bunches:
reduction by factor 1000
Train to train tolerance of final doublet
limiting the luminosity loss to 10%:
200nm
American Linear Collider Workshop, Baltimore, March 2001
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A TESLA Site near Hamburg
American Linear Collider Workshop, Baltimore, March 2001
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Cost
Project will be presented to the public at the TESLA Colloquium on March 23/24
including cost
American Linear Collider Workshop, Baltimore, March 2001
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A Detector for TESLA
Large detector for
Optimal tracking
Optimal energy flow
High central magnetic field (4T)
High granularity ECAL
High granularity HCAL
Both inside the coil!
Instrumentation down to
very small angles:
hermeticity!
Iron return yoke instrumented
as muon system
American Linear Collider Workshop, Baltimore, March 2001
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Detector Overview
Overall detector view:
Enlarge view of the
inner tracking system:
American Linear Collider Workshop, Baltimore, March 2001
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The VTX Detector
High precision detector close to the beam pipe (R(min) = 1.5 cm)
Several technologies are under discussion
Active pixel sensors (a la LHC technology)
CCD based sensors (SLD technology)
CMOS based sensors (new development)
SI ladders are "stretched"
The CCD version:
American Linear Collider Workshop, Baltimore, March 2001
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Central Tracking Detector: TPC
Sideview of the TPC
Fieldcage / TPC vessel:
Light composite walls
Modelled after ALEPH / ALICE fieldcage
Max Voltage: 100 kV
American Linear Collider Workshop, Baltimore, March 2001
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Readout Technology: GEMs
Use GEM (or similar) system for signal amplification and readout:
True 2−D readout possible
Compact, thin endplates
Mechanically "simple"
Gains > 10000 have been observed
Measured gain
in a 2−GEM
structure
American Linear Collider Workshop, Baltimore, March 2001
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Performance of the Tracking System
Overall tracking performance:
Full pattern recognition in
TPC, VXT, FTD, FCH
Sophisticated merging of
different subdetectors
Final clean−up step
Based on LEP software with
further developments
Efficiency > 98.5%
Secondary vertex finding
Based on SLD ZVTOP
Combined with OPAL NN approach
Tuned on Z−data
American Linear Collider Workshop, Baltimore, March 2001
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Calorimetry: ECAL
Both ECAL and HCAL are inside the coil
ECAL: fine grained SI−W calorimeter
Module length: 160 cm
transverse: 1x1 cm
longitudinal:
30 x 0.4 X W
12 x 1.2 X W
About 30 million channels
American Linear Collider Workshop, Baltimore, March 2001
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Calorimetery: HCAL
HCAL: "tile calorimeter" with iron as absorber, scintillator tiles as active medium
Readout of tiles with clear
fibres to a place outside the
barrel
16 fold symmetry in Phi
9 longitudinal samples
transverse sampling > 5x5 cm
Energy resolution
for tile
or alternative
digital option
American Linear Collider Workshop, Baltimore, March 2001
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Calorimeter Performance
Thorough evaluation difficult and needs significant software development
Some preliminary results:
The calorimeter is optimised
for the measurement of the
energy flow in the event:
Need exellent separation of
Mass resolution of
charged and neutral particles
the visible mass of
Excellent connection to the
the Z in hadronic
tracker information
Z decays
Excellent measurement of the
longitudinal shower shape
Goal: Energy flow resolution
of 30%
HHZ events:
separation of signal and
background for different
energy flow resolution
American Linear Collider Workshop, Baltimore, March 2001
a) LEPtype
resolution
60%(1+|cos θ|)
b) 30% resolution
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Calorimeter Performance
Separation of WWZ:
"
Standard performance
b) resolution 60%
American Linear Collider Workshop, Baltimore, March 2001
"
High resolution calorimeter
a) resolution 30%
Performance
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Backgrounds
Beam Beam backgrounds:
Pairs
Hadronic background
neutrons
10 simulated pair particles
Synchroton Radiation induced backgrounds
Beam gas backgrounds
Muon induced backgrounds
Per BX: 129000 pairs (360 TeV total energy)
Some numbers:
SIT/FTD: O(20) hits / detector
Photons into TPC: O(1300)
Occupancy O(0.1%)
Particles with E>3 MeV into
ECAL: O(200)
Hits from pairs/ BX on the vertex detector layers
American Linear Collider Workshop, Baltimore, March 2001
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Backgrounds: Neutrons
Simulation of neutron backgrounds:
FLUKA2000 & Pythia
Full detector model in FLUKA
Cross checked with Pythia
Some fluxes in the detector:
VTX
FTD
SIT
TPC
ECAL
HCAL
Yoke
<1E09
<2E09
<7E08
(1MeV)/year/cm2
15000/BX neutrons/BX
<10000/BX
<10000/BX
~55000/BX
Fluxes are not expected to be a problem
for detector components
American Linear Collider Workshop, Baltimore, March 2001
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Overall Detector Performance
Two particularly challenging examples:
determine the detailed properties of the Higgs
Reconstruction of the Higgs branching ratio
into different flavours, as a function of the
Higgs mass
American Linear Collider Workshop, Baltimore, March 2001
Reconstruction of the Higgs Potential
via ZHH events
Combination of high luminosity
and high precision detector allows
reconstruction of complete picture
eg of the Higgs.
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Detector Mechanics
First conceptual version of detector
moving and installation:
Open the endcap Yoke
Retract the endcap calorimeters
Move the TPC along z
Acces the inner detectors
Proposed cable routes out
of the detector
American Linear Collider Workshop, Baltimore, March 2001
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The TESLA Research Campus
Central laboratory site at km15
HEP experiment(s)
XFEL laboratory
Artists drawing of the HEP hall
Aerial view of Ellerhoop
American Linear Collider Workshop, Baltimore, March 2001
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TESLA: Goals and Milestones
Goals:
Develop superconducting technology
Use LINAC as driver for X−FEL
Milestones reached:
Routine production of cavities with > 25MV/m
Cavities with >40MV/m as single cell cavities
Construction and operation of TTF I
Stable operation for > 8600 h
Demonstrate SASE principle at <100 nm
Successful development of klystrons, RF couplers, etc
Development of the Physics Case
2 ECFA/DESY workshops with large and international
attendance (total >10 workshop meetings)
Milestone reached: TESLA TDR Part III (physics),
PartIV (detector), Part VI (other research options)
Continuation for two more years to
Develop the physics studies further
React to new developments
Continue work on the detector (R&D efforts are starting)
Continue the work on machine/ detector interface
American Linear Collider Workshop, Baltimore, March 2001
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TESLA: The Next Steps
Presentation to the public: TESLA Colloquium
Integrated HEP and FEL laboratory with site close to Hamburg
Including cost estimate
Detailed costing of accelerator costs
Based on industrial studies and the experience gained at TTF
The next steps:
Operation of TTF I, upgrade to TTF II (2003)
Formal proposal (TDR) March 2001
Evaluation of proposal by German Wissenschaftsrat during 2001
ECFA/DESY study on long term perspectives of particle physics
in Europe (2000/2001) with similar studies in US and Asia
ICFA study of the Global Accelerator Network concept (2000/2001)
Cryostat
Damping Ring
Input Coupler
SC Magnets
Cryogenics
Klystrons
INFN
INFN
IN2P3
Spain
TU Dresden
DESY
Modulators
DESY
Global accelerator Network
Laboratory
Operation, R&D
American Linear Collider Workshop, Baltimore, March 2001
Operation, R&D
Operation, R&D
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American Linear Collider Workshop, Baltimore, March 2001
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Conclusions
TESLA: a proposal for a new large
interdisciplinary research center
Most technical problem are solved
500 GeV baseline design is "conservative"
Energy upgrade potential is real
HEP experimentation at TESLA is
challenging
Needs serious and significant Detector
R&D
Combination of HEP and FEL offers
exciting new perspectives
Plans:
TESLA TDR now
German Wissenschaftsrat: 2002
International technical review?
American Linear Collider Workshop, Baltimore, March 2001
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A Global Accelerator Network
Construct and operate future large accelerators in the framework of a global network
Make projects part of the national programs of the participating countries
Maintain the scientific and technical culture and know how in home labes, remain
attractive for young people, yet contribute to and participate in large, unique projects
Maintain and run accelerators to a large extend from participating labs
Pull together world−wide competence, ideas, resources
Capital investment is done at home
Site selections becomes a less critical issue
Put accelerator close to an existing laboratory:
Make optimal use of existing experience, manpower, and infrastructure
Specific financial obligations for the host country
ICFA study findings:
Global considerations:
Need laboratory structure
Host nation is essential
Will bear a major fraction of the cost
American Linear Collider Workshop, Baltimore, March 2001
Technical considerations:
Project requires central management
Host lab will have safety responsibility
Remote operation is in principle feasible
Local staff of approx. 200 is needed
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