Transcript Fast Beam Diagnostics at the ILC Using the Beam Calorimeter

Fast Beam Diagnostics at the ILC
Using the Beam Calorimeter
Christian Grah, Desy
FCAL Workshop
12-13 February
Cracow
Contents
Very forward region and BeamCal
Beam parameter reconstruction
• Principle
• Results on 20mrad geometry with the nominal
ILC parameter set.
Summary and outlook
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
2
Very Forward Region
LumiCal: 26 < θ < 82 mrad
BeamCal: 4 < θ < 28 mrad
PhotoCal: 100 < θ < 400 μrad
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
3
BeamCal
e+
e-
e+e- pairs from beamstrahlung are
deflected into the BeamCal
 15000 e+e- per BX
=>
Deposited energy from
pairs at z = +365
(no B-field)
10 – 20 TeV
 ~ 10 MGy per year
 “fast”
=>
O(μs)
 Direct photons for q < 400 mrad (PhotoCal)
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
W:diamond sandwich calorimeter
4
Backgrounds (Old 20mrad Geometry)
Sketch of old BeamCal
geometry.
Projection of LumiCal‘s
inner radius.
Energy deposited
in LumiCal from pairs.
20mrad DID
 backscattering from pairs
hitting the LumiCal edge
(K.Büsser)
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
5
ILC B-Field Configurations
20mrad DID
(Ri(LumiCal) = 13.5cm)
(Ro(BeamCal) = 16.5cm)
20mrad AntiDID
(14mrad seems necessary
for AntiDID)
An AntiDID configuration is close to the headon/2mrad design.
BUT better be prepared for both possibilities.
DID: Detector integrated Dipole, B-field aligned with the incoming beam
AntiDID: B-field aligned with the outgoing beam
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
6
Fast Luminosity Monitoring
 Why we need a fast signal from the BeamCal?
 We can significantly improve L!
 e.g. include number of pairs hitting BeamCal in the
feedback system
3
x 10
34
Luminosity / cm-2s-1
Improves L by more than 12% (500GeV)!
2
position and angle scan
1
G.White QMUL/SLAC
RHUL & Snowmass presentation
0
0
100
200
300
Bunch #
FCAL Workshop Cracow,
12-13 Feb 2006
400
500
600
Luminosity development during first 600
bunches of a bunch-train.
Ltotal = L(1-600) + L(550600)*(2820-600)/50
C.Grah: Beamdiagnostics
7
Beamstrahlung Pair Analysis
 A lot of information is stored in the energy distribution of
beamstrahlung pairs hitting BeamCal.
 Observables (examples):
•
•
•
•
•
•
•
total energy
first radial moment
thrust value
angular spread
E(ring ≥ 4) / Etot
E/N
l/r, u/d, f/b asymmetries
 Beam parameters
•
•
•
•
•
•
•
•
•
•
σx, σy, σz and Δσx, Δσy, Δσz
xoffset
yoffset
Δx offset
Δy offset
x-waist shift
y-waist shift
Bunch rotation
N particles/bunch
(Banana shape)
FCAL Workshop Cracow,
12-13 Feb 2006
detector: realistic segmentation, ideal
resolution, bunch by bunch resolution
C.Grah: Beamdiagnostics
8
Analysis Concept
Beam Parameters
• determine collision
• creation of beamstr.
• creation of e+e- pairs
Observables
1st order TaylorExp.
guinea-pig
(D.Schulte)
+
Matrix
*
Δ BeamPar
Observables
Observables
=
Taylor
nom
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
• characterize energy
distributions in detectors
FORTRAN
analysis program
(A.Stahl)
and/or
GEANT4
Solve by matrix inversion
(Moore-Penrose Inverse)
9
observable j [au]
Coefficients of the Taylor-Matrix
parametrization
(polynomial)
slope at nom. value
 taylor coefficient i,j
1 point =
1 bunch crossing
by guinea-pig
beam parameter i [au]
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
10
Analysis for nominal ILC Parameters
single parameter analysis
Quantity
ILCNOM,
20mrad DID
FCAL Workshop Cracow,
12-13 Feb 2006
sx
sx
sy
sy
sz
sz
y
C.Grah: Beamdiagnostics
Nominal
Value
Precision
553 nm
old
4.8
3.9
new
2.9
7.4
5.0 nm
0.1
0.2
0.1
0.4
8.5
8.5
6.7
6.3
2.0
0.6
300 mm
0
11
2mrad and 20mrad Analysis
Nominal
Value
Quantity
sx
sx
sy
sy
sz
sz
Precision
553 nm
2mrad
3.1
5.2
20mrad
2.9
7.4
20mrad (2par)
2.8
7.6
5.0 nm
0.3
0.2
0.2
0.3
0.4
0.4
4.8
8.5
11.1
3.7
6.3
7.4
300 mm
εy
40x10-9mrad
1.7
2.9
5.2
εy
0
4.2
4.1
4.7
17.7
9.3
10
x
y
0
0.5
0.6
0.6
N
2x1010
0.01
0.01
0.01
N
0
0.01
0.02
0.03
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
...
12
Status of Analysis
GuineaPig files for ILCNOM ready
(~400 pair files).
New geometry ready.
Single and multiparameter analysis
started. Mostly done for
• 2mrad
• 20mrad DID
Good progress in the Geant4
implementation (A.Sapronov‘s talk).
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
13
Summary & Outlook
 Including a fast signal of number of pairs or total energy into the
feedback system can significantly increase luminosity of the
accelerator.
 Analyzing the spatial energy distribution of beamstrahlung pairs
hitting the BeamCal grants access to many beam parameters. For
highly correlated parameters measurements from other systems can
be included (e.g. PhotoCal).
 20mrad geometry is implemented with DID field approximation.
 ILCNOM investigation is in work.
 Geant4 simulation is running, BC observable calculation and beam
parameter reconstruction can be done with some limitations.
Next:
 Geant4 simulation with realistic b-field map and compare to
simplified one.
 Hopefully no fast shower simulation has to be included (cpu time
dependent). Fast shower simulation is implemented in Geant4 for
homogenous detector….
 Find most interesting regions (layers) in the BeamCal segments.
 Need background calculation for our 20mrad geometry.
FCAL Workshop Cracow,
12-13 Feb 2006
C.Grah: Beamdiagnostics
14