Transcript Cartiglia_LTex_CMSHPS

HPS: High Precision Spectrometer @ CMS
Basic goal: a detector to measure leading protons
IP5
In its full design,
HPS has two set of stations:
1) A closer one at 240m
2) A further one at 420m
Currently we are working on phase I, the detector at 240 m
HPS Basic Design: Tracking & Timing
Tracking
A tracking detector (silicon based) to measure position
Position and angle, combined with the beam magnets, allow to
determine the momentum of the scattered proton and in turn the
missing mass
For optimum results: two pockets ~ 10 meters apart:
Momentum reconstruction: Dp/p ~ 2 10-4
 Position precision of 10 mm
Angular resolution of 1-2 mrad
Possible start-up configuration: one single pocket
one pocket with several silicon planes, spread over 20cm
 track precision of 50 mm
HPS Basic Design: Tracking & Timing
Timing
Timing measurement (Cherenkov based) from both sides of CMS
allows to determine the vertex of the protons and reject pile-up
(proton from different pile-up collisions)
Vertex z-by-timing: ~ 2 mm
Time resolution ~10 ps
Segmentation for > 1 proton/bunch
Edgeless, active to ~ 200 um from pipe
Radiation hard: lifetime > ~ 1 year at LHC at 1034
Rate: 25 ns sensitivity
HPS Referencing Timing [RT]
How to synchronize two points separated by a significant distance?
LLNL adapting system demonstrated by SLAC for LCLS experiments:
RF cable with feedback to keep clocks synchronized at each end
-240m
Reference
generator
+240m
coax
Master Clock
Comparator
Master Clock
Comparator
coax
Reference
generator
Master LHC RF clock
Measured timing jitter = 1.2 ps/C
using LCLS spare system and 520 m
coax
=> well within HPS timing
requirements
To complete full system demonstration:
• Modify LCLS system to use 400 MHz (LHC
frequency)
• Measure performance using PECL gate with TDCs
AVA7RK-50
AVA750, HELIAX®
Andrew Virtual AirTM
Coaxial polyolefin jacket
HPS240 schematic
Proton beam line
Scattered
proton
Short pocket (20 cm): under
evaluation
Tracking
Long pocket ~ 70 cm:
Tracking ~ 20 cm
Timing 20cm + 20 cm
We are working on a simplified HPS version, with only one
pocket per side
HPS read-out
Foreseen installation LS1 to operate @ L = 1034 cm-2s-1,
<PU> ~ 25
Single-side occupancy : pp  pX
rate: many MHz
Double-side tagging: pp  ppX L1 rate: hundreds of kHz
240 m detectors are in time for Level 1 trigger, to be used
in combination with central event information.
HPS location
Where is the HPS going to be installed?
At 240 m the beam pipe is easily accessible
Need to be careful?
How delicate is the
resistor box?
HPS location
Bonus: we are near an alcove that we would like to use for our services
HPS Beampipe
- Hamburg Beampipe, ~ 60-70 cm long
- Lots of expertise in-house (Mimmo Dattola’s project)
- We would really like to avoid secondary vacuum
- No difference in performance
- We would like to have high precision BPM near HPS
Willing to use a uniform ATLAS-CMS design
HPS beampipe
Bellow
HPS pocket
Bellow
Copper coated for RF-shielding and Non-Evaporative Getter (NEG) coated
for vacuum pumping.
High quality prototype ready for testing:
• The best results were achieved for the pockets produced by electroerosion and then laser welded.
• Exploratory studies were carried out of production by electro-erosion
in one piece, without the need of the pocket welding
HPS pocket: deformation
Beam-pipe deformation without secondary vacuum
Numerical simulations, analytical calculations and laboratory measurements showed
consistent results, all indicating that this design will have a small impact on the total LHC
impedance budget.
Tapering of the beam pipe indentations is recommended because it does reduce the
impedance significantly
HPS detector box
Moving box
BPM
~54 cm
Bellow
HPS schedule
HPS @ 240 meter:
• Beampipe installation during LS1;
• Timing detectors to be installed at the end of LS1;
• Tracking installation schedule to be defined
• Services to be defined soon
Well advanced components:
Movable beam pipe - Timing detector
Reference timing system – Simulation
HPS@240 is a learning step towards HPS @ 420
Outlook
The HPS community is working toward the installation in 2014 of
the first station, HPS@240 m.
Additional discussions within CMS are planned for the June
collaboration meeting.
Possible connections with TOTEM
A draft document on the HPS is available at:
https://twiki.cern.ch/twiki/pub/CMS/HPSDocuments/hps_note.pdf