Target and Production MUTAC 21 July 1999

C.D. Johnson

CERN

Physics aspects

Pion production versus proton energy and material

Production beam

Capture

Engineering aspects

Target damage - thermal, mechanical. chemical, dynamical

Target options and choice of material

Beam dump

Activation and shielding

Containment

Pion kinetic energy, T, in GeV From: H. Kirk

dN/dT p

er

GeV

per

inte

ract

ing

pro

ton

Target and Production MUTAC 21 July 1999 cdj

16 GeV/c protons on tungsten

Collect from this region

We aim to collect and deliver to the first phase rotation channel 0.6 pions of each sign per proton of 16 GeV/c.

In the region of low kinetic energy shown opposite this can be achieved by immersing the production target in a 20 T solenoid field of 75 mm radius. Pions of both signs having transverse momentum of up to 225 GeV/c are focused into the decay channel via the matching channel.

Note that the pion velocity varies from 0.68 to 0.98

Target and Production MUTAC 21 July 1999 cdj

Atomic mass A Solenoid field B, (T)

Tilt angle (mrad)Target radius (cm)

Meson yield( + ) fromdifferentin a solenoidfield, B ofaperture, Ra

as calculated by the

MARS code

Target and Production MUTAC 21 July 1999 cdj

Target and Production MUTAC 21 July 1999 cdj

Target and Production MUTAC 21 July 1999 cdj

FLUKA98

pion production

J. Collot, ISN Grenoble

Target and Production MUTAC 21 July 1999 cdj

Target and Production MUTAC 21 July 1999 cdj

Preliminary - H. Kirk

Target and Production MUTAC 21 July 1999 cdj

H. Kirk

Target and Production MUTAC 21 July 1999 cdj

H. Kirk

Target and Production MUTAC 21 July 1999 cdj

Production beam:

Fast cycling synchrotron

Pulse repetition rate: 15 Hz

Bunch length: z = 1 ns (to preserve polarization)

Intensity: 5 1013 p/ bunch (two bunches per pulse)

Beam momentum: 16 GeV/c ( production vs machine issues)

Beam size at target: r = 4 mm

Power in Beam: 4 MW

Power absorbed in target: 400 kW

Energy deposited in target: 27 kJ per pulse

Peak energy density in beam: 5 kJ mm-2 per pulse (ACOL beam was: 12 x greater)

Target and Production MUTAC 21 July 1999 cdj

Schematic of target station - liquid metal jet is injected in beam direction and is collected in a reservoir that also absorbs a large fraction of the dumped beam power

mercury dump

pions

Target and Production MUTAC 21 July 1999 cdj

CERN High power targetry for pbar production - solid target

A liquid mercury jet target was built but never used

CERN and Fermilab gained considerable experience in coping with target damage

Target and Production MUTAC 21 July 1999 cdj

proton beam

Hg jet

Schematic of beam/target interaction region. Hg jet radius: 7.5 mm, velocity 6 to 10 ms-1 *

*Question: is this high enough to penetrate the solenoid field?

B= 20 T

Target and Production MUTAC 21 July 1999 cdj

Optional target scheme devised by B. King using a rotating Cu/Ni band

Target and Production MUTAC 21 July 1999 cdj

ANSYS simulation of magnetohydrodynamics Changguo Lu, Princeton

The interaction of a liquid-metal jet with a magnetic field

This has been studied by:

K. McDonald, R. Palmer and R. Weggel

For a conducting jet in a strong magnetic field, eddy currents cause reaction forces that may disrupt its flow. The forces are proportional to the square of the jet radius (see opposite). This places an upper limit on the jet radius and a lower limit on the jet velocity needed to penetrate the solenoid end-field.

The analysis of a jet crossing the solenoid axis (as desired) is complex. This. and the computer simulations. will be tested by experiment.

Target and Production MUTAC 21 July 1999 cdj

REXCO simulations of contained and free-jet mercury targets - CERN ACOL project. Simulation predicts unreasonable negative density (pressure) waves and this leads us to doubt the predicted expansion of the free jet at ~103 ms-1.

1 kJ of beam energy deposited at time zero. Target length: 50 mm Beam radius (uniform density) 0.5 mm

Target and Production MUTAC 21 July 1999 cdj

Recent simulations of pressure waves inside Gallium and Mercury jets made by

Ahmed Hassanein, ANL, (HEIGHTS code)

Cylindrical jet, radius 10 mm

Gaussian proton beam, 2.5 1013 protons, r=4 mm

Jet edge velocity - mercury jet Radial oscillations inside Gallium and Mercury jets

Target and Production MUTAC 21 July 1999 cdj

Recent simulations of pressure waves inside Gallium and Mercury jets made by

Ahmed Hassanein, ANL, (HEIGHTS code)

Cylindrical jet, radius 10 mm

Gaussian proton beam, 2.5 1013 protons, r=4 mm

Note on target heating

Temperature rise along the jet axis for protons of 16 GeV/c is estimated to be be in the region of 300º C. Protons of 2 GeV/c would raise the axial region to ~750º C, i.e. well above the boiling point of mercury (357º C)

The HEIGHTS code predicts that the jet will not break up when the beam passes - needs benchmarks.

ACTIVATION

Proton flux: 3 1015 protons cm-2 s-1 Si old units

After 1 month of use the specific activityof a heavy metal fixed target (3 ) would be: = 3 1013 Bq g-1 And the total activity: = 5 1015 Bq 1.3 105 Ci

This value for the total activity would applyto the band-saw target and to the Hg jet.

The dose rate at I m from a fixed target or thecompressed band saw (1 day decay time) = 100 Sv h 104 rem h-1

The total activity of volatile spallationproducts (e.g. xenon, iodine) would be: = 1013 Bq 270 Ci

These would be captured in filters of the target enclosure vacuum system.

The extremely high induced activity levels may well provide the overriding reason for the useof a mercury jet target. Mercury has no long half-life isotopes. So mercury could be distilled to remove most non-volatile spallation products. There is a wealth of experimental experience in the use of mercury - cite: G Bauer ESS.

Target and Production MUTAC 21 July 1999 cdj

Multiply by 9 for the dump

Target and Production MUTAC 21 July 1999 cdj

Radiation downstream from the target - the beam dump must extend at least 1 m into the matching section

Target and Production MUTAC 21 July 1999 cdj

G. Bauer gave an account of the ESS studies on liquid-metal spallation source targets (Hg chosen) at the recent -Fact99 meeting in Lyon, France.

http://lyoinfo.in2p3.fr/nufact99/talks/bau1.jpg

While these studies concern enclosed liquid cooled targets, much of the technology overlaps with our target requirements

Target and Production MUTAC 21 July 1999 cdj

G. Bauer ESS

Target and Production MUTAC 21 July 1999 cdj

Target and Production MUTAC 21 July 1999 cdj

Target and Production MUTAC 21 July 1999 cdj

G. Bauer ESS

Target and Production MUTAC 21 July 1999 cdj

Air actuator

Pressure reducer

Electro-pneumatic valve

Air line - 8 bar

trigger

Pneumatic valve - 5 mmPiston

pump

Observation chamber 10-1 Torr

to vacuum pump

V1

Single Continuous

shot pulsed jet 15 Hz

V1 triggered openModel liquid-metal jet target

CERN 1999

Target and Production MUTAC 21 July 1999 cdj

Model jet target cdj 06/99

Target and Production MUTAC 21 July 1999 cdj

Target and Production MUTAC 21 July 1999 cdj

This topic is one of the priority items for experimental R&D

This will be reported by Kirk McDonald

A target station engineering study is also needed.

Graham Stevenson, CERN

and

Helge Ravn with Jacques Lettry ISOLDE/CERN

are interested in participating.