cbm beam pipe - sts integration current status and plans

S. Belogurov et al., ITEP, Moscow CBM STS-beam pipe integration, JINR, 21.05.09

CBM beam pipe - STS integration current status and plans

Sergey Belogurov, Andrey Chernogorv, Alexander Semennikov ITEP, Moscow, Serguei Igolkin S-PbSU

Outline

- Design and integration• Reminder: Infrastructure in the magnet• Vacuum chamber: target and MVD • Beam pipe previous experience, options• Beam pipe – STS junction• STS module conceptual development• FEE integration and cooling• Station installation • more about the last station

- Simulations- Conclusions


Reminder: Infrastructure in the magnet

- Design from inside to outside (should be)- Power lines, data links, piping infrastructure are not under practical consideration yet.


Target: (multiple or single layer)

Reduce rescattering of heavy probes, narrow beam is needed

Otherwise possible to spread the beam and separate tracks from simultaneous or closely pie-lapping events. Concerns also beam-pipe (later)

MVD no layout available – affects design of the beampipe.

•Vacuum chamber: target and MVD


LHCb VELO 800 mm diam. 2 mm Al alloy, machined from a forged billet together with a bellow, NA61 – kevlar+mylarДобавить соображений

Beam pipe: previous experience


Beam pipe: options

We assume still that beampipe should be thin. The candidate material is Be. Can be easily machined down to 0.7 mm (~0.5 mm C) thickness, to 0.5 mm with an effort. For thinner objects foil is available.

“NPO Kompozit” is interested to manufacture the scientific object for price close to net cost.

Initially we consider the convex shape. At our thickness it should be mechanically stable. However we‘ll investigate also the concave option


Beam pipe: options

The problem of the stress release: bellows at the neck of the pipe, at the wide flange of the vacuum chamber, somewhere downstream; window 2x50 – good also for the experiment reconfiguration

Open issue: stability of the window vs. width of the beam, anyway not worth than for the target. No radiation swelling at 1022 n/cm2


FEA simulation of a cylinder for material budget minimization. Will be an open structure. Is it possible to have the single size of cylinder for all the station? Beampipe is

anyway inside the 2.5 °. 8-th

station 2.5 ° – 87 mm, max tube for the cylinder (middle rib not cut) is 56 mm. Seems yes, simulation is in progress.

Beam pipe – STS junction


How to overlap sensors, how to cool them (gas or tubes)? Gas cooling – small material, low temperature (evaporated LN2 – no hail). A lot of tricky mylar foils for correct flux organization, tubes are more easy.

STS module conceptual development


FEE integration and cooling

Ruby ball for torque less fixation.

Thermal contact of FEB to heatsink

Soldered tubes and plate or milled groove

with compound


Station installation

Note big additional height due to current mechanics. Approximation to 8-th station ~1600 mm (1). What can be reduced – cable between FEB and the last sensor; height of the heat sink;


Linear bearing NB SEBS-15BYM-UU-2-T1-430-P-W2

Station installation into mainframe


Station installation

Note. For the first 2 or 3 stations another kind of support should probably be developed

Height for the price of width. Gap of 1400 mm seems comfortable for mechanics. Possibility to match 1300 mm will be studied.


more about the last station

It was discussed by Iouri: for operation without MVD, even for primary vertex localization, one may need better vertical resolution. May be achieved by rotating some (e.g. the first and the last) of the

stations by 90° – the answer: concerning mechanics – no problem. Existing type of ladders may be used


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Simulations

First exercise with cbmroot. Look at hit density for several beampipes. 25 AGeV central UrQMD.

“thin” window vs. “normal” window


Msc, rad 0.7 mm Be

10 GeV/c

1GeV/c

At 5 cm

200 MeV/c

At 5 cm

0.8e-4 0.8e-3 0.04 mm 0.4 e-2 0.2 mm

95 1.2e-4 1.2e-3 0.06 mm 0.6e-2 0.3 mm

99 2.7e-4 2.7e-3 0.15 mm 1.5e-2 0.7 mm

99.99 1.3e-3 1.3e-2 0.6 mm 0.07 3.3 mm

StationWindow

Average dist. ~ 1/√ (hit density); 4 cm-2 → 5 mmA kind of figure of merit is desirable for design. Try to understand better the tracking algorithm


Al 3mm / Vac

Be 0.7 mm / Vac

1,111014 0,994123

1,136652 1,034718

1,164674 1,026648

1,143778 1,002507

1,193516 1,034837

1,198585 1,031623

1,225382 1,035851

1,277145 1,034435

1,348276 1,040394

1,411954 1,070166

2,032355 1,1017

St 4 ↓1,556383 1,058923

1,5233 1,022409

1,536732 1,03973

1,578947 1,011149

1,559915 1,015376

1,654725 1,05952

1,722108 1,024158

1,837522 1,023026

2,001253 1,020825

2,784404 1,072903

4,535676 1,134579

1,075201 1,00197

1,114579 1,029601

1,126935 1,020124

1,12739 1,011472

1,124965 1,018328

1,207553 1,050575

1,254574 1,055094

1,462934 1,117703

St 1 1,082289 1,05215

1,096257 1,042781

1,096702 1,044978

1,093855 1,028779

1,07158 1,017232

1,071932 1,03385

1,088287 1,012006

1,080266 1,016215

1,091689 1,026032

1,149883 1,080863

1,210858 1,140166

1,07118 1,019155

1,084971 1,017121

1,087632 1,021011

Al 3mm /

VacBe 0.7

mm / Vac

Thin window Normal window

Look at hit density in “square” rings vs. beampipe configuration.Results (higher effects at bigger radii) are not obvious at fingertips – to be checked carefully, may be soft deltas in the field?

Simulations

Total (St.1) thin w. Norm. w.

Vac. 790 790

Al 3 mm 963 1137

Be 0.7 mm 829 830


Conclusions• There is a temptation to build a cheap and thick beam pipe. To be carefully

studied in order to avoid late vain regrets.• Beam pipe design depends on MVD. Too early for fixing. However design of

junction between beam pipe and STS seems to be understood.• For choosing the sensors cooling method one has to evaluate the negative

effect of the tubes with cooling liquid along the ladders. Liquid cooling is much easier than the gas one.

• What is the profit in the STS physical performance due to current positioning of the stations in comparison to uniform one (each 10 cm). Is current positioning optimal? 7-th and 8-th station can’t be placed closer than 10 cm to each other without a big effort, is it acceptable?

• If necessary, concerning mechanics, modules can be mounted horizontally.• Current understanding of the STS mechanics require a magnet gap of 1400 mm,

we’ll try to match 1300 mm. Is it possible to evaluate price and field “quality” for both otions?

cbm beam pipe - sts integration current status and plans

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