C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Design and Tests of a New Rest Gas

Ionization Profile Monitor Installed in the SPS as a Prototype for the LHC

BIW04 May 3-6, 2004 –Knoxville, Tennessee

C. Fischer, J. Koopman, D. Kramer, R. Perret, M. Sillanoli

CERN – Geneva - Switzerland

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Acknowledgements

AT/VAC/SL: monitor conditionings ES/MME & PH/TA1: coatings D. Cornuet and Co.: magnet measurements G. Arduini: monitor insertion in SPS A. Beuret: magnet power supplies A. Guerrero: software requests B. Dehning, F. Roncarolo: wire scanner data

and all others….

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Outline

The New Monitor magnet central detector tank and assembly

Commissioning in 2002

The year 2003 problems & cures results

Preparation & Perspectives for 2004

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

New Rest Gas Monitor Encouraging results were got since the installation in 1999

of a prototype provided by DESY and modified to use signal from electrons.

It has been decided to equip the LHC with 4 gas monitors (one H, one V, in each ring).

Continuous profile measurements also needed in the SPS for the LHC era.

Prototype design compatible with LHC requirements: transverse space contingencies → compactness

impedance budget → no big discontinuities in the tank smooth transitions,

e- signal → B field required Conventional magnet found with 200 mm gap, fulfilling

space requirements

new gas monitor designed accordingly, manufactured in 2001 and installed in the SPS for the 2002 run

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

New Rest Gas Monitor: the magnet (1)

magnet recuperated from LEP with following characteristics:

Imax = 55 A

B max= 0.25 T

Strength = 0.14 Tm

Gap width : 200 x 200 mm2

Overall length 680 mm section: 681 x 646 mm2

hole drilled through the yoke for the light signal extraction

3D view

top view

200 mm

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

New Rest Gas Monitor: the magnetCham p Bo au centre de l'aim ant en fonction du courant

0

50

100

150

200

250

300

0 10 20 30 40 50 60 70I [A]

Ch

am

p [

mT

]

Variation sur l'axe Z avec Y = 0 e t déplacem ent sur X pour I = 55 A

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

-100 -80 -60 -40 -20 0 20 40 60 80 100

Z [m m ]

Ecar

t [%

]

x = -75 mm x = -50 mm

x = -25 mm x = 0

x = 25 mm x = 50 mm

x =75 mm

Variation sur l'axe Z avec X = 0 et déplacem ent sur Y pour I = 55 A

-1.6

-1.4

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

-100 -80 -60 -40 -20 0 20 40 60 80 100

Z [m m ]

Eca

rt [

%]

Y = -75 mm Y = -50 mm

Y = -25 mm Y = 0

Y = 25 mm Y = 50 mm

Y =75 mm

% %

Relative B variation along z with y=o at different x

Relative B variation along z with x=o at different y

B linearity

I (A)

B (mT)

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

New Rest Gas Monitor: mechanical designThe central detector

166 mm

84 mm

cross section view

top view

3D view

e-

light

MCP

prism

light

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

New Rest Gas Monitor: mechanical designThe tank within its magnet

200 mm=84 mm

Light signal

cross section view

3-D view

Light signal

680 mm

e- signal

side view

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

New Rest Gas Monitor

Picture of the assembled

central detector

As installed in the SPS

with 2 corrector magnets used at - B/2 (3 magnet bump)

Electric field map

e_

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Results from commissioning in 2002 encountered problems: high noise level electron cloud effect with LHC type beam

evidence : signal increase after injection of 3rd batch

effect : electrode DC voltage fluctuations →signal fluctuations

high frequency modes generated by the LHC beam structure inside the detector and in cables

effect : HV instabilities, signal loss

remedies during 2003 stop NEG application (TiZrV) on HV electrodes to lower SEY RF absorbers (filters) close to HV supplies series resistors close to detector feed-throughs view port conducting cover plate installed for better image

current conduction

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

The 2003 campaign (1)

encountered problems and cures: bad electrical contacts on phosphor screen after bake-out at

200 C (needed for NEG activation) insertion of thin CuBe frame with flexible contacts aging of MCP central region due to high output signal (test of a fast but less sensitive phosphor) MCP gain decreased and image intensifier added, bump applied to the beam orbit to avoid bad area limited resolution camera lens diaphragm opening reduced by 50%

lightening on phosphor screen with shortest bunch length series resistors removed image tilt due to stray B field (through the magnet hole ) on the

image intensifier

intensifier wrapped with metal sheets magnet used at 50% of B max

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Results from 2003 (1)

Pilot: 5.109 p Nominal: 3.5.1013p

= 0.88 mm

450 GeV

= 0.83 mm

E= 450 GeV

LHC type beams from pilot to nominal investigated; dynamic in current 104

n=3.5 10-6 m

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Results from 2003: analysis (3)limitations: electron cloud effect still there (from 3rd batch) → signal increase

saturation of MCP at 450 GeV

Profile Norm evolution along the cycle

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Results from 2003: analysis (4)Limitations, ct’n

limited resolution, show-up at 450 GeV for low beam dimensions (s ≤ 0.7 mm)

75 ns LHC beam: n= 1.4 10-6 m pilot bunch: n= 0.65 10-6 m

26 GeV – IPM= 1.5 mm

450 GeV - th IPM = 0.36 mm

meas IPM = 0.57 mm

450 GeV - th IPM = 0.53 mm

meas IPM = 0.64 mm

26 GeV – IPM= 2.2 mm

Error contribution: 0.35 mm

Sources: intensifier

residual tilt

tails

optics: 247 m /pixel

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Cures implemented during the 2004 stop (1)

Electron cloud: MCP input face NEG coated

MCP aging and saturation:

MCP replaced by a new one, will be operated at lower gain coupled with Low Light Level camera → lower MCP output current suppression of 2 stage amplification → better S/N ratio and resolution more sensitive phosphor layer on new prism: → lower MCP output current

CdS:In →Y3Al5O12:Ce (P46) variable gain to be applied during acceleration cycle → to avoid saturation

Resolution limitation:

general cleaning of different detector parts replacement of external RF absorbers close to power supplies number of wires on cathode grid decreased by factor 3 → contribution to tails non reflective treatment of support surfaces → to suppress parasitic reflections new optics in front of the camera → improved opening

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Cures implemented during the 2004 stop (3)

new optical bench

LLL

camera

PM tube

C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

Perspectives for 2004

With these improvements and a few other upgrades of the

control software, all efforts will made during the year 2004 to bring the monitor to an operational stage for the LHC era.

A second monitor working in the H plane is approved and is expected for the 2006 SPS start-up.

Thank you for your attention