1

LHC Upgrade

Abe SeidenUC Santa Cruz

8th International “Hiroshima” SymposiumTaipei December 5-8, 2011

Special Session in Honor of Professor Takashi Ohsugi

2

The LHC has now completed a very successful run, with ATLAS and CMS having collected about 5 fb-1 of data at 7 TeV center-of-mass energy. The data set allows us to search for the simplest versions of supersymmetry up to 1 TeV and to cover a large fraction of the mass range up to about 500 GeV for a Standard Model Higgs.

This is the beginning of an ambitious program to fully explore the multi-TeV mass range. We expect to collect about another 20 fb-1 of data next year and then the machine will be shut-off for about 2 years to allow operation at 14 TeV center-of-mass. Whatever is found by a year from now we will want significantly larger amounts of data. The LHC has demonstrated that it is able to deliver very large amounts of data and the capabilities of the detector must be enhanced to benefit from this data. This leads to a program of detector upgrades. I will discuss the upgrades for ATLAS, of which I am a member, but CMS has an ambitious program for upgrades as well.

3

The general plan for upgrades, following the machine improvement plan, is expected to look as follows: Approximate Time Frame Goals Data collection: 2011-2012 25 fb-1 of data collected at 7 TeV center of mass Shutdown: 2013-2014 Install new inner pixel layer Data collection: 2015-2017 100 fb-1 of data collected at 14 TeV center of mass Shutdown: 2018 Upgrades focused on trigger Data collection: 2019-2021 300 fb-1 run at 3 x design luminosity Shutdown: 2022-2023 Install new tracker, new calorimeter electronics Data collection (HL-LHC) 3000 fb-1 collected to study physics at multi-TeV

Goal for first upgrade (2018 installation) is to improve trigger to maintain trigger thresholds at about 25 GeV pT and also add hardware track finder to be used after level 1 trigger decision to enable better participation of tracking in event selection. Also will install detectors far along beam pipe to tag outgoing protons, allowing some unique new capabilities.For second upgrade (2022 installation, to enable runnning at 5x design luminosity) most ambitious item is a completely new tracker likely based entirely on silicon technology. Much work on this is already in progress given the long time period needed to develop new components and then for actual construction. Will discuss the new tracker further below.Have already had a first look at physics at 7 TeV, no “easy” discoveries yet, will require large integrated luminosity to utilize the full potential of the LHC for physics!

ATLAS Experiment ATLAS Experiment

4

5

Present ATLAS Inner Tracking Detector

2018 trigger upgrade will use silicon hits to find tracks via stored patterns. For HL-LHC, tracker will be replaced and full volume will be filled with silicon tracking layers

6

Some of the Special Challenges for the Present ATLAS Silicon Tracker:

• Had to cover large area so cost per module had to be kept down.• Fast (25 nsec) readout to have single beam crossing sensitivity.• Cooling to maintain silicon detectors below room temperature to avoid thermal runaway.• Tight alignment tolerances (5 -10 microns between stereo pairs).• Low mass supports, cables, fiber readout.• Had to run at high voltage (500 or more volts) to maintain charge collection. Required careful design of electrodes to avoid micro-discharge. A few microns here or there matter a lot (crucial work by Prof. Ohsugi)!

For HL-LHC tracker, survive about 10x larger dose:• Have to develop different silicon detector to maintain charge collection after much larger fluences. Have to tolerate even higher voltages (perhaps1000 volts).• Many more channels, so many system issues have to be dealt with, cannot scale up cable plant to match channel count. Must also reduce frontend power consumption. Develop integrated readout structures and new powering method (serial powering or DC-DC converters) to save on cable material. Strip length reduced in inner part of detector (short strips, about 2.5 cm long) to reduce occupancy and strip capacitance allowing a noise reduction (provides high efficiency even with reduced signal collection)

The illustrations below give some feeling for the scale of the challenge at the HL-LHC. The first plot is of tracks resulting from simulation of a new design for the inner tracker with 5 superimposed collisions (corresponding to luminosities already surpassed by the LHC); the tracks are easy to separate. The second plot shows an event with 400 simultaneous collisions. (Plots from Abdel Abdesselam, June 2010. These are (r, z) projections of generated tracks). The plots assume a new tracking detector, perhaps the largest and most challenging single item of the HL-LHC upgrade. Some key parameters are occupancy (even if it looks busy, a low occupancy can allow good tracking), having enough layers to validate tracks, and minimizing material to limit conversions and hadronic interactions.

7

Fluence in the HL-LHC sATLAS Tracker

ATLAS Radiation Taskforce http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/RADIATION/RadiationTF_document.html

5 - 10 x LHC Fluence

Mix of n, p, depending on radius R

sATLAS Fluences for 3000fb-1

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E+17

0 20 40 60 80 100 120

Radius R [cm]

Flu

en

ce

ne

q/c

m2

All: RTF Formulan (5cm poly)pionproton

Pixels

Radial Distributionof Sensors determined by Occupancy < 2%.

ShortStrips

LongStrips

Design fluences for sensors (includes 2x safety factor) :B layer (r=3.7 cm) 2.5*1016 neq/cm2 1140 MRad Innermost Pixel Layer (r=5cm): 1.4*1016 neq/cm2 712 MRad 2nd Pixel Layer (r=7cm): 7.8*1015 neq/cm2 420 MRad Outer Pixel Layers (r=11cm): 3.6*1015 neq/cm2 207 MRad Short strips (r=38cm): 6.8*1014 neq/cm2 30 MRad Long strips (r=85cm): 3.2*1014 neq/cm2 8.4 MRad

Strips damage largely due to neutrons

Pixels Damage due to neutrons+pions

8

9

Pixel & SCT geometry models: Endview of Barrels

Has enough hits to find most tracks and keep “fakes” to a small level.

Strip Pattern: Upgrade ATLAS07 n-on-p SSD, able to handle high voltages.

Al

SiO2 +Si3N4n+

Detector Development for New TrackerFor pixels slim edge 3-D detectors and slim edge hybrid pixel detectors have been developed and will be deployed in the new inner pixel layer. This provides a good start toward pixels for a future HL-LHC detector.For HL-LHC inner pixel layers probably 3-D detectors, outer layers slim edge n-on-p detectors, same technology as strip detectors. Have been developing the n-on-p detectors, with an eye toward minimizing cost (compared to n-on-n detectors), and collection of electrons to maintain signal.

10

Proton Irradiation of ATLAS n-on-p detectors: Validates Design

• Irradiations performed to 2.3, 6, 13×1014 n cm-2 with 70 MeV Proton

11

Good agreement between different sites, systems, analyses and measurement techniques.

Factor of 10 improvement in radiation lifetime, also much improved annealing behavior with n-on-p sensors.

Measured noise of module with Hamamatsu sensor and 20 ABCN chip hybrid of 650 e-. Collected charge matches goals.

12

10 cm x 10 cm detector unit segmented electrically into 4 short-strip detectors.

FE-I4B, Production Chip for New Inner Pixel Layer, Important Step toward HL-LHC Pixel Electronics

Rate Capability Largest chip in HEP, results in large cost reduction in pixel systems since dominant cost is bump bonding where cost ~ 1/Chip Area. Designed by large collaboration of ATLAS institutions.

13

14

Concluding Comments Over more than a decade the LHC has afforded the

particle physics detector collaborations the opportunity to participate in the development of:

1) Advanced superconducting magnets and the highest energy accelerator in the world.

2) Many novel particle detection techniques for the ATLAS and CMS detectors.

3) A new distributed computing model for data analysis by international teams.

4) An enhanced model for international collaboration in particle physics research.

We can anticipate that the continued development of the LHC into the higher luminosity HL-LHC will afford continued opportunities and challenges for the detector collaborations while simultaneously allowing the exploration of the TeV mass range.