Transcript 2010-04-08 LEPP meeting Dan Peterson

2010-04-08 LEPP meeting
Dan Peterson
ILC highlights : Development of a TPC for the ILD detector at the ILC
There are some significant differences
between an e+e- experiment (ILC, CESR, LEP) and a pp experiment (LHC).
At the ILC, the reduced noise in the detector opens tracking options
that are not possible at the LHC;
ILD uses a TPC.
(OK, Alice uses a TPC, but that is different.)
The experiments drive the detector requirements;
measurement of the recoil mass of l+ l- in (e+ e- HZ, Z l+ l-) drives the resolution;
particle Flow Analyses requires a hermitic detector (98%).
I will touch on the reasons for what we (LCTPC collaboration) are doing.
Then describe the “highlights” what I have been doing this year.
ILC TPC Large Prototype
The International Linear Collider
(ILC) is planned for commissioning
in after 2015. Electron-positron
collisions will have 500GeV c.o.m.
energy.
Detectors, like the ILD are
being planned by
international collaborations.
One of the two
certified detectors employs a
Time Projection Chamber (TPC)
for recognizing tracks and
measuring the momentum.
A “large prototype”,
representing a
small section
of the final TPC,
will be operated in
2008-2009
(2009 – 2011).
(from a poster for “graduate student night” 2006)
The Cornell group built the endplate
for the TPC large prototype.
Current work is an extension of the
previous endplate development.
30-October-2008,
Endplate, fully assembled,
with Micromegas module
in center location.
30-October-2008
The leak test, on the field cage:
With 42 o-rings, and 8 pipe threads,
the leak test passed.
(from a presentation at a Linear Collider workshop, 2008-11-15 )
measure the mass recoiling against l+ l- in (e+ e- HZ,
Z l+ l-)
δPt / Pt2 = 2 x 10-5 /GeV
recoil mass resolution is dominated by other effects
δPt / Pt2 = 4 x 10-5 /GeV
recoil mass resolution is starting deteriorate
δPt / Pt2 = 7 x 10-5 /GeV
recoil mass resolution is dominated by momentum resolution
(from a Journal Club, 2006-January )
Meeting the resolution goal δ(1/Pt) < 3 x 10-5 / GeV
requires a point resolution of ~100μm,
but more importantly,
requires a knowledge of the magnetic field ∫ δ(Br) dz ~ 20 μm
construction can deliver ~20 mm (not μm), mapping can deliver ~2 mm.
The improvement must come from track-based magnetic field calibration.
For magnetic field calibration to converge,
we must have a non-track-based calibration of the detector positions ~ 50 μm.
We must have the stability of the detector positions ~ 50 μm
(from a Journal Club, 2006-January )
There are processes where WW and ZZ must be separated without beam constraints
(example e+e-  nnWW, nnZZ ).
Particle Flow Analysis provides must jet energy resolution of about
dE/E = 30% / E1/2
The energy resolution goal of the Particle Flow Analysis constrains the
material in the endplate of the TPC, which is in front of the forward calorimeters.
This is not the LHC; this is a 98% hermetic detector.
At this time, the leading thought is that the material limit for the TPC endplate
including structure, detector modules, electronics, and cooling,
is 15% XO .
That is a summary of our development goals:
detector placement and stability at the level of 50 μm (achieved by the 2008 endplate)
endplate material ~ 15% XO (not achieved by the 2008 endplate).
Progress this year has been in
building and comparing CAD models
of possible replacements for the
current Large Prototype endplate,
which will provide input for designing the ILD endplate.
mass material deflection
kg
%X0
microns
stress
Mpa
(yield: 241)
LP1
18.87
16.9
33
1.5
8.93
8.0
68
3.2
Al 7.35
(Al-C hybrid) C 1.29
7.2
Space-Frame
7.5
Lightened
(all aluminum)
Lightened
8.38
< 168*
< 4.8*
(* values for the aluminum only)
23
4.2
Material: space-frame has slightly more material than the Al-C hybrid.
Deflection: space frame is more rigid than LP1,
~3x more rigid than the lightened (all Aluminum),
and > 3x more rigid than the Al-C hybrid.
Space-frame model
Lightened outer rim
LP1 stiffening ring is removed.
Cut-outs in
radial machine tool direction
leave material for strut mount.
Lightened Uninstrumented Area
5mm thickness as in hybrid
Sheet back-plane
simple landing for strut mount
removes adjustment of back-plane
Between-Row Struts
term change, these are now “struts”
not the major load carriers in the
ILD endplate
and can be low density
In-Row Struts
major load carriers in ILD
higher density
Outer circumference struts
termination as in ILD
Strut properties
All struts are adjustable.
All parts are Aluminum.
Machined mount
bolted to the front and back plates
Adjustment screw
10-24 (m4.8-1.06) on one end
10-32 (m4.8-0.91) on the other end
sensitivity is 150 micron/turn
As modeled, the screw is 4mm, which
is approximately the stress diameter.
Spanning Rod
As modeled, is 6mm solid,
but could be 8mm hollow.
Deflection
Maximum is 23 microns
Back-plane locally warps
±5 microns
The inside surface is smooth.
Back-plane twists at 3-point
intersections. This feature
will carry over to the ILD.
Not optimized:
back-frame distance
back-frame thickness
vs strut density (spacing)
strut thickness