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The MERIT experiment at the CERN PS. MOPC087 WEPP169 WEPP170. Leo Jenner. Overview. MERcury I ntense T arget Experiment Purpose of Experiment Experimental location and set-up Data Particle generation / detection Target stability Summary & Achievements.

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The merit experiment at the cern ps

The MERIT experiment at the CERN PS




Leo Jenner


  • MERcuryIntense Target Experiment

  • Purpose of Experiment

  • Experimental location and set-up

  • Data

    • Particle generation / detection

    • Target stability

  • Summary & Achievements

A proof-of-principle test of a target station suitable for a Neutrino Factory or Muon Collider source using a 24-GeV proton beam incident on a target consisting of a free mercury jet that is inside a 15-T capture solenoid magnet.

Proposal submitted to CERN – May 2004

Experiment approved as nTOF11

Participating Institutes

  • BNL, MIT, ORNL, Princeton University


  • Study jet disruption by varying the PS spill structure

    MERIT: 180 J/g (+25°C)

Target velocity

  • 1-cm diameter Hg jet, jet velocity  20m/s

  • Hg jet/proton beam configuration:

    • Hg-jet ↔ solenoid axis = 33 mrad

    • proton beam ↔ Hg-jet axis = 67 mrad

    • beam ↔ Hg-jet interaction length = ~30cm (2.1 lI)

      Proton beam

  • 24 (14) GeV/c extracted from PS

    • Max. intensity 3  1013 protons/pulse (30TP)

    • Beam spot r 1.2 mm rms

    • Variable pulse length 0.134  700 msec

    • ~100 high-intensity pulses

    • 3  1015 protons on target in total (radiation limit)

Solenoid velocity

Target chamber

Hg-jet hydraulic system

Hg container

Proton Beam


Left – 30cm – 15cm – magnetic centre – 15 cm - Right

TT2/TT2A: MERIT velocity

PS ring


Beam Dump

IR is enclosed in solenoid to capture pions velocity

15 T, liquid N2 cooled, copper

Interaction length optimised to reduce re-interaction

Cooling Stresses: 50MPa / 200MPa

Simulation velocity




Simulation: MARS velocity

Particle Detection:


PIN Diode


80 velocityμsec/frame

Disruption Length increases rapidly in no field velocity

Disrupted material moves faster with no field

14 GeV velocity

24 GeV

  • Disruption length @ 24 GeV is about 20cm for 10-15T field

  • For a 20m/s jet, 28cm (2lI) can be renewed in 14ms

    • rep rate of 70 Hz possible

    • equivalent to 8 MW of beam power

    • neutrino factory baseline = 1 MW

Summary velocity

  • The break up of the Hg jet is influenced by the magnetic field.

    • The splash velocity increases as the beam intensity increases, however, magnetic field reduces the effect

    • The Hg jet disruption length is suppressed by magnetic field.

  • The 24 GeV proton beam tends to result in a longer disruption length than the 14 GeV proton beam.

  • The magnetic field stabilizes the Hg jet flow.

    • The fluctuations on the jet surface decreases as the magnetic field increases.

  • The field tends to keep the jet size constant as it moves downstream

  • The longitudinal Hg jet velocity was not affected by the magnetic field.

  • The MERIT experiment took beam as scheduled for three weeks in autumn 2007 at CERN PS

  • All systems performed well, the run with beam was very smooth and the whole scientific program was completed

  • The experiment was dismantled in winter 2007 with its components put in temporary storage for cool-down at CERN waiting to be shipped back to US

  • The primary objective to conduct a successful and safe experiment at CERN was amply fulfilled

  • Important results validating the liquid metal target concept are already available, more to come as the analysis progresses

  • The MERIT experiment represents a big step forward in the targetry R&D for high power targets.

References: in autumn 2007 at CERN PS

  • Neutrino Beams from Muon Storage Rings: Characteristics and Physics Potential, S. Geer, Fermilab-PUB-97/389

  • The MERIT High Intensity Liquid Mercury Target Experiment at the CERN PS, I.Efthymiopoulos et al, MOPC087, EPAC 08

  • The MERIT High-power Target Experiment at the CERN PS, H.G. Kirk et al, WEPP169, EPAC 08

  • A 15-T Pulsed Solenoid for a High-power Target Experiment, H.G. Kirk et al, WEPP170, EPAC 08


  • Thesis: Development of a Beam Condition Monitor System for the Experimental Areas of the LHC Using CVD Diamond,

  • Juan Luis Fernández-Hernando

    • Chapter 9 - Simulation of the worst accident scenario with a test beam