Jaarvergadering NNV Secties K&H, Lunteren, November 7, 2008 1 Highlights from the Large Hadron...

Jaarvergadering NNV Secties K&H, Lunteren, November 7, 2008 1

Highlights from the Large Hadron ColliderHighlights from the Large Hadron Collider

Jos Engelen

CERN

•Physics at the Terascale•The LHC: brief overview and status•The LHC experiments: brief overview and status


Standard Model and Beyond(?)

x8

gauge

The Supersymmetric world? One supersymmetric partner for each ‘standard’ particle –the Higgs sector becomes slightly more complicated: 5 supersymmetricHiggs bosons

HThe Higgs sector – ‘the unknown’ Hqq

mqq

mll

mHHZZWW

gHh

HhHmHL qq

qql

l

WHH )()2)(

cos2

1(

44)(

2

1

,,

222

243222


The ‘Standard Model’

is a wonderful model for describing the fundamentalparticles and fields and their interactions, it provides aquantitative description of all experimental results so far, but:

•the model invokes a mechanism for dealing with mass: it is an empirical fact that certain field particles (W, Z bosons) carry mass, incorporating this in the theory is highly non-trivial – it requires the introduction of a new field (Higgs field) and corresponding particle (‘the Higgs’): this particle has never been found by an experiment it will be at the LHC•the model would ‘go wrong’ at high energy without the Higgs particle (or other ‘new physics’)•‘unification of forces’ at very high energy could be revealed by a new trend setting in at LHC energy: ‘supersymmetry’


‘The Terascale’

Based on ‘extrapolations’ from our presentunderstanding and on quite general theoreticalinsights we expect the ‘new physics’ to manifestitself at an energy around or below 1 Tera-electronVolt = 1012 electronVolt, i.e.at the Terascale accessible at the LHC for the first time(and only at the LHC for years to come!)

Jaarvergadering NNV Secties K&H, Lunteren, November 7, 2008

Quark Gluon Plasma

The LHC will also provide Pb Pb collisions at574 + 574 TeVallowing unique contributions to the studyof a quark gluon plasma


Accelerator and Experiments

Undergroundcircular tunnel27 km circum-ference; 100 munderground

4 caverns forexperiments ()

x

xx

x

RF

BD

ATLAS

CMS

LHCb

ALICE

*


Accelerator

Collisions of 7,000 GeV on 7,000 GeV protons(for reference: proton mass = 1 GeV)

Luminosity 1034 cm-2s-1

(collision rate normalized to cross section)

Innovations: ‘2 in 1’ superconducting 8.3 T dipoles (operating temperature 1.9K) focusing s.c. quadrupolesChallenges: collimation (350 MJ stored energy per beam, can melt 800 kg of copper) and furthermore the mere size of the system, e.g. more than 33,000 tonnes of ‘cold mass’, 27 km of cryogenic distribution line, etc.


Accelerator complex

(1959)

Biggest ring = 27 km circumference


R&D

pre-production

industrialproduction

1232plusspares


Van streng tot kabel

NiTi filamenten, 7(geproduceerd viaextrusie)


In the tunnel

Magnetinter-connect

Quality controlandQuality assurance


6 superconducting bus bars 13 kA for B, QD, QF quadrupole

20 superconducting bus bars 600 A for corrector magnets (minimise dipole field harmonics)

42 sc bus bars 600 A for corrector magnets (chromaticity, tune, etc….) + 12 sc bus bars for 6 kA (special quadrupoles)

13 kA Protection diode

To be connected:

• Beam tubes• Pipes for helium• Cryostat• Thermal shields• Vacuum vessel• Superconducting cables

Magnet Interconnect


In the tunnel

Jumper connectingcryogenicdistributionline and magnets(once every~100 m)

(early photo,tunnel practicallyempty)


In the tunnel

Beam deliverytowardsinteractionpoint

Current distributionusingHigh TemperatureSupercondutorcurrent leads


LHC Status

Installation complete•cryogenic distribution line•injection lines•sc dipoles and quadrupoles; interconnect•inner triplets preparing beams for collision•RF stations (sc) for acceleration 450 GeV 7000 GeV•beam dumps•collimation•beam instrumentationHardware commissioning•cool-down complete•pressure tests •powering testsCommissioning with beam•circulating beamsColliding beams•Restart Spring 2009


The Large Hadron Collider project saw a wonderfulstart of operations on September 10, 2008:

•LINAC, Booster, PS, SPS were accelerating beam to 450 GeV for injection into the LHC•The injection lines (TI8, TI2) transported the beam to the LHC•The injection kickers sent the beam(s) into the LHC•Circulating beams, in both apertures, were established for the first time, with the whole world looking over our shoulders, in a matter of hours•The LHC experiments were ready and operational as planned and recorded beam related (timing!) data immediately•The Worldwide LHC Computing Grid was up and running

Start of Operations


Start of Operations

During the days following September 10 someunreliable (‘old’) elements of the electricalinfrastructure (transformers) had to be repaired/replaced,but the preparations for collisions continued, one othervery important milestone was passed easily, not becauseit was easy but because of excellent preparations:

the RF system captured the beam

the road to first beam-beam collisions was now fully open


Final Hardware Commissioning

The magnets in Sector (‘Octant’) 34 had not beencommissioned yet to full current for operationat 5 TeV (i.e. commissioning to 5.5 TeV)

The 7 other octants of the LHC had been commissionedto 5 TeV (and well above) without problems

On September 19 (around 11:18) an incident occurred,leading to a large Helium leak in sector 34 – cold Heliumescaped into the tunnel, the insulation vacuum was broken(up to vacuum barriers), the beam vacuum was broken(up to sector valves)


Recovery Sector 34

It is now clear that recovery of Sector 34 will takeuntil (‘into’) the planned (and obligatory) Wintershutdown – LHC operations will restart Spring 2009.A precise planning is being worked out.

The nature of the incident has been understood– it is due to an electricalfault (resistive splice in interconnect)

The loss of the insulation vacuum lead to some collateraldamage – the logistics of the repair program are beingworked out. Very importantly: diagnostic tools are being designed toavoid such problems in the future


Schedule of Experiments

The experiments will now go into ‘long shutdown’ mode,to be ready again in early Spring 2009: a more precisedate will be agreed with them as soon as this is possible

Most experiments have identified a useful and/or necessaryprogram of work of 4 – 5 months: repairs, refurbishments,improvements, additional installation work

Everybody involved in the LHC project is as motivated asever (or more motivated than ever) to overcome thistemporary setback! Everybody has reacted professionallyand with determination.


The successful start-up

The behaviorof the beams was excellent and understood


Cross-section of LHC cryodipole


Cooldown Status


Cooldown Status


RF cavities


The RF cavities and transverse dampers

Courtesy Edmond Ciapala

Preparation for BeamRF synchronization in place – clocks and timing now going from SR4 to all users. Recent successful dry run tests with all users and OP group, including basic software.

Procedures for beam commissioning well defined.

Longitudinal diagnostics in good shape to study and commission first beams….

Fibre-optics signal distribution from RF in SR4 to Experiments, BT & BI equipment and to CCC.

40 MHz bunch clocks, revolution frequencies,40 MHz 7TeV reference. Injection & dump kicker pulses


Synchronisation

PSB

Re-phase withbeam ~50ms

Re-phase withbeam ~20ms

Rephase with beam: The timedifference between the targetbucket FREV and the source

bucket FREV is measured by aTDC. The TDC value then

changes the RF frequency sothat they come in line.

This takes time to complete, anddisturbs the orbit.

RF frequency isnearly fixed. Justjump to the nextbucket. This can

only happen if theSPS is empty

FillingLHC Ring 1

LHC RFSR4

R1 Bucket fromtelegram

SPS

SPS RFBA3

CPS

CPS Sourcebucket FREV

Next SPS targetbucket FREV

Timedifferenceto digitalconvertor

VCO CPS RFRF

Batch 3 Batch 4 Batch 5

Injection Kicker

OutIn

Target BucketFREV

LHC TBF LHC TBFSPS SBF SPS SBF

SB-Frev jumps tothe next LHC TB-Frev

Target bucketrevolution frequency

Kicker tail is to long to allowinserting batch 4 between batch

3 and batch 5

+-

Referencefrequency

Batch number to Bucket numberconversion

Bucket = K + h/nh = 35640 RF Buckets

n = 12 BatchesK = 121 Approx (Offset)

Courtesy Roger Bailey


Injection Region


08 08 08

Friday 15:20Beam on to TI2 TEDMSI etc pulsingCycle LHC Sector 23

OP Beam down TI2 first shot

Friday 19:00

TI2 TED out, beam to TDI, kickers offGive Alice 20 minute warning before taking TED out

INJBeam on TDI after correction end TI2

Friday 21:00Kickers on, time in, position checksResolve timing issues

INJ

Interesting collaboration between timing and RF

Friday 21:40 TDI out - threading - momentum matching - beam to IR3 Jorg & team

Beam to IR3 first shot. Tweak SPS.

Courtesy Roger Bailey


First Trajectory


Kick response compared with theoretical optics


Dispersion 2-3

The trajectory of the off-momentum (1 per mil) beam. On the far left is the end of TI2 where there are no measurements. It goes through LSS2 and Alice with practically zero dispersion. In the arc there is a slight mismatch which is of no consequence and LSS3 it perfectly maps the large dispersion bump from positive to negative that is designed to stop uncaptured particles (which will be lost as the field rises since they are not accelerated) on the collimators.The vertical dispersion (bottom) is zero as it should be.

Lyn Evans – EDMS document no. 964651 33

Lyn Evans – EDMS document no. 964651

Beam on turns 1 and 2

34Courtesy R. Bailey


Few 100 turns

35Courtesy R. Bailey


Dump dilution sweep

36


No RF, debunching in ~ 25*10 turns, i.e. roughly 25 mS

37Courtesy E. Ciapala


Capture with optimum injection phasing, correct reference

38Courtesy E. Ciapala


The LHC experiments haveseen first ‘man made’ beam

ALICE Detector

TPC

PHOS

Muon arm

TOFTRDHMPID

PMD

ITS

ACCORDE


Injection tests

y = 3.5326x - 12525

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

200000

0 10000 20000 30000 40000 50000 60000

ITS multiplicity

FMD

mul

tipl

icit

y

Series1

Linear (Series1)

SPD/SSD, Sunday, 15.6Dump on TED

SPD hits versus bunch intensity(beam through ALICE)

FMD hits versus SPD hits(beam through ALICE)

FMD event display(1 bunch through ALICE, > 100 000 hits)


Single turn

Double turn, beam 1 back at point 2 !

Luminosity monitor (V0)


Trigger timing (before alignment) versus bunch numbersingle shotfor SPD, V0, beam-pickup BPTX, T0 triggers

Auto-correlation for SPD trigger, with multi-turn correlations (3564 bunch crossings)

Beam pick-upT0SPDV0

First interactions 12th September

ITS tracks on 12.9.2008

Circulating beam 2stray particle causing an

interaction in the ITS

24/10/2007 23rd RRB J. Schukraft

TPC

ParticleIdentification

Momentum Resolution

Krypton Gain Calibration

46

LHCb Spectrometer

VELO

RICH1

TT

Magnet

OT

RICH2 Calo. System

Muon System

LHCb sees tracks from the LHC injection tests

Silicon tracker

Muon chambers

VELO(Run 30933, Event 14)

SPD (provided trigger)TED events

Beam1 induced OT tracks originating close to the beam pipe


ATLAS

45 m

24 m

ATLAS superimposed tothe 5 floors of building 40

LHCC, 24-Sep-2008, PJ

Status of ATLAS

7000 Tons

50Very first beam-splash event seen in ATLAS (as seen online in the ATLAS Control Room) on 10-Sep-2008 at 10:19


51

A busy beam-halo event with tracks bent inthe Toroids from the start-up day (offline)

52

Barrel-tracks

TRT in the run 22-25 August (a cosmic shower)

Shower


The CMS Detector


Calorimeters: Collimators Closed

Energy in ECAL (EE-, EB, EE+)

ECAL: Splash events provided a source for overall internal synchronization.Crystals were time aligned to within 1ns !


WLCG

Since CCRC08 in May the experiments have continued to run work at very high levels on the grid infrastructure and continued to keep data

transfers running at a level consistent with that expected in data taking. WLCG has seen cosmic data and also the first “events” from LHCb during

the second injection test, and data sets from all 4 experiments on Wednesday 9/10. The transfer rates all summer have been in excess of 1 GB/s more or less continuously with higher peaks (the data taking rate is

650 MB/s, twice that for safety). This, and the continuous high rate of job submission has been driven by experiment functional testing, and

more and more detector-driven stress tests.


Conclusions

The LHC experiments have followedthe remarkable performance of theLHC machine with an equally remarkableperformance:

the detectors work with real beam!


Conclusions

Recovery of Sector 34 has the highest priority

Start-up in Spring 2009 is now the target

And then: a two phased approach to SLHC

Date post:	31-Mar-2015
Category:	Documents
Upload:	meadow-wootten
View:	218 times
Download:	1 times

Jaarvergadering NNV Secties K&H, Lunteren, November 7, 2008 1 Highlights from the Large Hadron...

Documents