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Status of the Roman Pot Project reminder prototyping & testbeam mechanics & infrastructure simulation. Hasko Stenzel ATLAS week October 2006. Roman Pots for ATLAS. RP. RP. RP. RP. 240m. 240m. IP. RP. RP. RP. RP. MAPMTs FE electronics & shield. PMT baseplate.

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Status of the Roman Pot Project

  • reminder

  • prototyping & testbeam

  • mechanics & infrastructure

  • simulation

Hasko Stenzel

ATLAS week

October 2006

Roman Pots for ATLAS













FE electronics

& shield

PMT baseplate

optical connectors

scintillating fibre

detectors glued on

ceramic supports

10 U/V planes


Roman Pot Unit

Roman Pot

H.Stenzel, October 2006

testbeam: October 3-18


Verify detector performance observed in 2005 at DESY (6 GeV e- ) with

new(larger) detectors, new ATLAS-type electronics with a high energy beam.

New prototypes:

  • 10 planes, U&V, 16 fibres  tracking

  • 2 planes, U&V, 64 fibres  final geometry

  • 2 overlap detectors, 120 fibres each  alignment

  • trigger scintillator  elastic L1


  • hit multiplicity & efficiency

  • cross talk

  • spatial resolution & homogeneity

  • edge sensitivity & active surface

  • alignment performance with overlap detectors

  • trigger efficiency & uniformity

H.Stenzel, October 2006

detector prototypes for testbeam 2006

2 x 2 x 30


2 x 2 x 64

construction studies

10 x 2 x 16

resolution studies

  • Fabrication of prototypes at cern bt PH/DT2

  • with support from Lisbon (LIP) for

  • fibre machining, aluminum coating, QC

  • testbeam mechanics

  • and from Giessen for

  • gluing of fibres

  • optical connectors

H.Stenzel, October 2006

QC: Metrology

Fibre ends of 10_2_16

after machining at 45º

< 20µm variation from one plate to another

prototype 2005:

> 250 µm variation

H.Stenzel, October 2006

overlap detector: new technology

Section to be bent

Straight section

Preheat from room temp to 85ºC

Bend fibres at 85ºC

A. Mapelli

H.Stenzel, October 2006

trigger scintillator

New design of trigger

scintillator with lightguide

coupled to a PMT.


light guide


H.Stenzel, October 2006

electronics: final set-up


H.Stenzel, October 2006

electronics: testbeam set-up

CERN, Orsay (MAROC) & Lund (PMF & MB)

PMF Build Up for testbeam October



Active board

MAROC R/O chip

MAROC chip

Adapter board

HV board

H.Stenzel, October 2006

The final ATLAS Roman Pot Unit

  • Pre-production of one unit at Vakuum Praha

  • expected at CERN Oct.31

  • will be instrumented and tested

  • review of the tests before production

  • possible timescale : 4 units at CERN April-May 2007

H.Stenzel, October 2006

Pre-production unit

Courtesy of

Vakuum Praha

H.Stenzel, October 2006

The final Roman Pot

Pumping hole

Top flange with helicoflex joint

Brazing under test S.Mathot (TS-MME)

Rectangular body out of center

Overlap extrusions brazed on bottom

  • Prototyping & production at CERN TS

  • Material for prototype & final production arrived Oct.2

  • Prototyping Oct/Nov 2006

  • final production sync. with Unit procurement

H.Stenzel, October 2006

Infrastructure: Cable installation

Reminder – cabling list:

H.Stenzel, October 2006

Infrastructure: Cable installation

Installation of all cables through UPS galleries is now completed on both sides of IP1

  • Access to the UPS galleries is not allowed anymore due to the installation and calibration of the instruments for the geometers.

  • HV multiconductor cables are to be installed, different path via US to UX, depending on the location of HV power supplies (US15)

Air-core cables – min. bending radius of 250mm respected

Optical fibers

H.Stenzel, October 2006

Q4 polarity switch

RR13 Level 1

inverter 7kA

Switch for Q4 quadrupole to change its

polarity when switching from normal to

ATLAS/Lumi optics.

Base & cabling are completed.

Temporary Cu plates ordered, will be

installed soon

Buying the switch itself can be done later



RR13 Level 0


Christophe Coupat AB/PO

H.Stenzel, October 2006

Simulation of the LHC set-up

elastic generator


with coulomb- and ρ-term

SD+DD non-elastic

background, no DPE

beam properties

at IP1

size of the beam spot σx,y

beam divergence σ’x,y

momentum dispersion

ALFA simulation

track reconstruction


luminosity determination

later: GEANT4 simulation

beam transport


tracking IP1RP

high β* optics V6.5

including apertures

H.Stenzel, October 2006

Simulation of elastic scattering

hit pattern for 10 M

elastic events simulated

with PYTHIA + MADX for

the beam transport

t reconstruction:

  • special optics

  • parallel-to-point focusing

  • high β*

H.Stenzel, October 2006


distance of closest

approach to the beam

Global acceptance = 67%

at yd=1.5 mm, including

losses in the LHC aperture.

Require tracks 2(R)+2(L) RP’s.

Detectors have to be

operated as close as

possible to the beam in

order to reach the coulomb


-t=6·10-4 GeV2

decoupling of L and σTOT

only via EM amplitude!

H.Stenzel, October 2006


The t-resolution is

dominated by the

divergence of the

incoming beams.

σ’=0.23 µrad

ideal case

real world

H.Stenzel, October 2006

L from a fit to the t-spectrum

Simulating 10 M events,

running 100 hrs

fit range 0.00055-0.055

large stat.correlation between

L and other parameters

H.Stenzel, October 2006

experimental systematic uncertainties

  • Currently being evaluated

  • beam divergence

  • detector resolution

  • acceptance

  • alignment

  • beam optics

  • ΔL/L ≈ 1.9-2.1 %

  • missing: background studies

  • (are under way)

  • total error ≈ 2.6-2.8 %

H.Stenzel, October 2006


  • testbeam 2006 is starting, preparations in full swing

  • new prototypes produced, including overlaps and trigger

  • electronics set-up close to ATLAS

  • RP units and pot prototypes are under production

  • major cable installation effort

  • progress on simulations for TDR

H.Stenzel, October 2006