Status ReportBeam Working Group

11 February 2005

• Alternative optics • MAMUD• CEDAR• Fluka simulations

Main topics treated since December:

Niels presented first results on a study of an alternative 2-stage optics. Normally a charged beam is designed with two big bends in the same direction, the first one creating the dispersion that allows momentum selection and the second one recombining the selected momenta. The I229 design has been based on a achromat consisting of 4 dipoles.

A priori the muon background situation looked more advantageous in the traditional 2-stage design, however halo studies show that in the end muon backgrounds are in fact harder to control.

Also the 2-stage design is incompatible with NA60 (time-scale!) and would

require a displacement of the blue tube and Helium tank, the spectrometer and the Liquid Krypton calorimeter.

In view of the tremendous practical implications of the 2-stage optics, we agreed that we would not pursue it for the moment, but see whether some of the good aspects of this optics can be integrated in the achromat-based design.

The question can be reconsidered in case the Liquid Krypton would not be used.

Alternative beam optics and design

Niels Doble

Proposed Dipole configuration

Pole gap is 2x11 cm V x 30 cm H

Coils cross section 10cm x 20cm

M.Losasso

New design of MAMUD

Magnet rough parameters

Total weight ≈ 150 ton

Overall Dimension 2.6 m x 2.8 m x 5.25 m (WxHxL)

Number of iron plates (2x) 150

Coil Current ≈ 3.6 KA

Total power dissipation ≈ 0.43 MW

Field integral on axis (from -1 m to +6.2 m)

6.25 T m

Magnetic field into a “good field region”

(by 10 cm x 10 cm)

≈ 1.1 T

M.Losasso

Better treatment of forces

Main results of simulation

Magnetic field at magnet centre

Field integral on axe - Packing factor is 0.54

30 cm

22 cm

M.Losasso

1. A realistic timescale of the magnet project is something about 3 y. 6 months for conductor development, 1 y for coil production, 1 y for coils assembly, 6 months for contingency

2. Depending on personnel activities at the specified time, the coils could be produced at CERN with tools and machines that are mostly already available (the saving in costs however is relatively low)

3. The assembly costs (and time) shall not be overlooked. For such a construction my rough approximation is that 20% of the total have to be added to take

care for these charges. 4. The operating costs have to be evaluated (power, cooling,..) with reference to

different scenarios (duration of experiment, projected cost of the electricity and of other infrastructures).

5. A structural analysis have to be done to define a practical way of keeping in position the constructed plates (under g and em forces

M.Losasso

Preliminary cost analysis

• Iron 300KEuro approximately

• Coils 120 KEuro

(cost of Al coil construction + a ‘guesswork’ amount to keep into account the welds and the higher complexities of the winding)

• Cu conductor cost is to be evaluated, but my first guess is that will be around 150 KEuro (100KE was the AL conductor cost)

M.Losasso

ONLINE

Preliminary

OFFLINE

PRELIM

INARY

+ Adapt to new layout of MAMUD+ Take away beam pipe

CEDAR

•Suggestion to use H2 instead of He: less Xo (N.Doble)

First discussions with SC/GS have taken placeNo showstopper yet

•Realization that 50 MHz per PM is untolerable (A.Placci)

Have to divide rates over many detectors.A.Placci suggests 3 alternatives to PM’s:

- Microchannel PM’s with 64 anodes of 6x6 mm2 eachbut only few out of 64 channels would be hit

- Linaear Array Multi-Anode PM’s- Silicon PMT’s (Dolgoshein et al) with 1000 pixels of 30 m2

•Original construction drawings have been recuperated

•Optics simulation studies are under way (L.Gatignon)

Nicely matched dimensions and # channelsBut : common dynode, cost

Looks very suitable.

But very high noise rate(up to 1 MHz/mm2) at room temp.Has to be cooled to about -70oC.

Remains to be optimized for blue light(wave length shifter?)

Some validations for CEDAR-N

Situation Rdiaphr diaphr Spot PM

Monochromatic pencil beam K+ 100.0 0.333 7 x 24 mm

Monochromatic pencil beam + 103.0 0.341

Monochromatic pencil beam protons 909.0 0.314

Beam spot 10 mm in each plane 100.0 0.330

Beam divergence 0.1 mrad in each plane

100.0 0.517 7x24 mm

Momentum spread 1% 100.0 0.343 7x24 mm

‘Nominal beam’ (1%, 0.1 mrad, 10 mm)

100.0 0.524 7x24 mm

Cedar-N, 10.69 bar of Helium, 75 GeV/c, diaphragm 10 mm

PM plane at Z = 706 mm, diaphragm at 1251 mm, quartz window at 851 mm

Monochromatic pencil beam K+ 100.0 0.333 7 x 24 mm

‘Nominal beam’ (1%, 0.1 mrad, 10 mm)

100.0 0.524 7x24 mm

For Hydrogen at 2.61 bar:

90 92 94 96 98 100 102 104 106 108 1100

500

1000

1500

2000

2500

3000

3500

4000

Radial distance of at diaphragm [mm]

Diaphragm 1mm

+K+

Nu

mb

er o

f en

trie

s

3 mm

Ring at correct position-K separation as expected:

8 Condensors “focus”the photons on the PM’s

Simulation allows tocalculate the image sizeand to optimise locationof the photon detectors

Next steps for CEDAR:

• Complete simulation studiesInclude dependence of Cerenkov angle (deliberately ignored so far)

Detailed analysis of performance with Hydrogen gas

Add detailed simulations of multianode PM’s and Silicon detectors

• Try to organise some testsSee whether one can borrow or buy a Hamamatsu PM (cost!)

Organise a test of some Silicon PM’s

• Think about electronics and readoutFast “OR” or more complicated ‘majority logic’?

FLUKA Studies for vacuum requirements

Ingredients:

1) FLUKA: hadron-nucleus interaction with Oxygen p-O, p-O, K-O

2) TOY Monte Carlo: propagate final state particles across geometry of 1st Straw

plane + 15 Veto planes

ie. 14 large angle anti + {medium angle PV,LKr,SAC}

3) basic analysis with generated variables (no resolution smearing)

G.Collazuol

G.Collazuol

Assuming no particle identificationGain order of magnitude with CEDAR

CEDAR is really required !!!

Demanding !!!Leak rate in straws?Stainless steel tank?…..

Final remarks

• Updated beatch geometry listings are available on te WEB

• First discussions on possibilities for neutral beam for 2006

• Work will and must continue