NuMI

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)

Limits for NuMI PrimaryBeam Loss
November 11, 2003

NuMI

NuMI Primary Sensitivity toBeam Loss

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)The combination of:• very intense NuMI primary beam« 4E13 ppp, 120 GeV, 1.9 sec spilland• unshielded transport thru protected aquifer region« Nancy Grossman presentation

lead to requirement for a low beam loss NuMI
primary transport line.
Have done detailed MARS modeling and beam loss
study to understand beam loss limitsNuMI

MARS Beam Loss Studies

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)• Extensive MARS14 beam loss study by S. Striginov, I.
Tropin, M. Kostin, N. Mokhov. Combined with studyof groundwater flow near NuMI transport tunnel (N.
Grossman,et.al), results set limits on allowed beam loss
along NuMI primary beam
• Tunnel residual activity is also calculated for different
beam loss modes• Beam loss modes considered include loss along eachcomponent for normal transport with varying beamemittance, effects from power supply instabilities, andpresence of wire scanners inserted into the beam

NuMI

Lambertson Region Component
Modeling

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)

NuMI

Detail of Tunnel Geometry

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)

NuMI

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)

Extraction & Pretarget Enclosures

Extraction Enclosure
156 mrad down-bendPretarget Enclosure
98 mrad up-bend & target focus

NuMI

Regions for Calculation ofStar Density DistributionsNBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)NuMI

Bean Size (500 pi envelope)vs Apertures

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)NuMI

Beam Loss for Magnetic Field
Variations

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)NuMI

Normal Tune:
Fractional Beam Loss

Comparison of beam loss for original andcurrent beam optics

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)

NuMI

Maximum Acceptable Loss in
Different Regions – Groundwater

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)NuMI

Beam Loss Limits from MARS14
Calculations

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)• Results indicate average beam loss fraction limits ofseveral ⋅10-4 to ⋅10-3 of the high intensity primary beamflux, dependent on tunnel location. A loss fraction limit of
10-6 of the beam is seen in lined regions of the carrier
tunnel. However, in this region geometry constraints
preclude direct primary beam loss except for fault modes
such as a vacuum pipe collapse or a magnet coil failure.
• Maintaining average beam loss fraction levels at ~ 10-4 orless is also well matched to need for control of component
residual activity. Sustained localized beam loss of thislevel leads to ~ 1.50 mSv/hr readings on near magnet
outside surfaces.

NuMI

System for Beam & Beam Loss
Control

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)• Most important is a well functioning beam transport line
« Apertures / optics design enabling clean beam transmission,
minimal sensitivity to normal variations of beam parameters emittance, momentum spread, bunch rotation, etc.
« Quantitative understanding of Main Injector extracted beam
parameters.

• Power supply stability« Design for long term ~ 60ppm for major bends, 200ppm forsmaller bends. (One supply at these limits gives < 1 mm change
along transport, 0.25mm for targeting.) Pulse to pulse variations
are much less.

• Comprehensive loss monitor coverage« Sensitivity to all beam loss modes, redundancy of loss coverage,
continuous checks for loss monitor function, calibrated responseand dynamic range for fractional beam loss from 10-5 of the highintensity beam to a full beam loss

NuMI

System for Beam Control (cont)

NBI03
Nov. 7-11, 2003
MARS Primary Beam Loss
S. Childress (FNAL)• Capability for precise and rapid correction of beam position
problems due to system drifts« AUTOTUNE beam position control• Comprehensive alarms and limits monitoring• Comprehensive beam permit system to preclude beam
extraction to NuMI when an identifiable problem exists« Beam test prototyping of hardware ongoing in MiniBooNE and AP0lines

All of these are patterned after previous successful efforts.