# INTRODUCTION

This report contains a description of the design of the technical
components of the Neutrino at Main Inject (NuMI) project at Fermilab as
well as a summary of radiation safety considerations. The technical
baselines for the NuMI Project have already been established and can be
found in the NuMI Facility Technical Design Report, issued in October
1998. The NuMI Project was baselined in November 1998. In October 2001,
revised cost and schedule of the NuMI Project were submitted as NuMI
Baseline Change Proposal. This baseline Change Proposal was approved in
January 2002. This report updates and expands upon the scope and the
design of technical components in the NuMI Facility after the Baseline
Change Proposal.

The NuMI Facility Project produces an intense beam of neutrinos to
enable a new generation of experiments whose primary scientific goal is
to definitively detect and study neutrino oscillations. The beam is of
sufficient intensity and energy so that experiments capable of
identifying muon neutrino (ν~μ~) to tau neutrino (ν~τ~) oscillations, as
well as other possibilities, are feasible. Although not a primary goal,
the intense NuMI beam could also support a strong program of neutrino
scattering physics of interest to both the Elementary Particle Physics
and Nuclear Physics communities.

The first step in the production of the NuMI neutrino beam is to direct
a beam of protons from Fermilab's Main Injector onto a production
target. Interactions of the proton beam in the target produce mesons,
which are focused toward the beam axis by two magnetic horns. The mesons
then decay into muons and neutrinos during their flight through a long
decay tunnel. A hadron absorber downstream of the decay tunnel removes
the remaining protons and mesons from the beam. The muons are absorbed
by the subsequent earth shield, while the neutrinos continue through it
to a "near" detector (in a new experimental hall at Fermilab) and
beyond, to the "far" detector in Soudan, Minnesota. The Fermilab and
Soudan experimental halls house massive detectors specially designed to
detect the small fraction of the NuMI beam neutrinos that interact in
them. This experiment is called MINOS (Main Injector Neutrino
Oscillation Search).

The NuMI Facility includes the underground enclosures (tunnels and
halls) as well as two service buildings located on the surface. The NuMI
beamline and experimental facility at Fermilab are fully described in
the NuMI Facility Technical Design Report. The layout of the NuMI
Facility underground enclosures is illustrated in **Figure 1-1.** An
aerial photograph of the Fermilab site with the beamline superimposed is
shown in **Figure 1-2** and the trajectory of the neutrino beam between
Fermilab and Soudan is shown in **Figure 1-3**.

![](media/image1.png)

Figure 1-1 Layout of the NuMI Facility.

![](media/image2.jpeg){width="6.560416666666667in" height="8.2in"}

Figure 1‑2 Aerial view of the Fermilab site and the NuMI beamline.

![](media/image3.png){width="5.6194444444444445in" height="1.19375in"}

> ![](media/image4.png){width="4.903472222222222in"
> height="5.908333333333333in"}

Figure 1‑3 Trajectory of the neutrino beam between Fermilab and Soudan,
Minnesota.

# Scope and parameters 

The scope of the NuMI Technical Components is laid out in **Table 1-1**
and described in more detail in Chapter 2. Key parameters of the
beamline are listed in **Table 1-2.**

  ---------------- ------------------------------------------------------
  **Subsystem**    **Description**

  Primary Beam     Extraction and transport of 120 GeV proton beam from
                   the Main Injector to the NuMI Target

  Neutrino Beam    Production and focusing the secondary beam from the
  Devices          NuMI target through the focusing horns

  Power Supply     Power supplies, cables and connections for NuMI
  Systems          beamline elements

  Decay Region &   Decay pipe for neutrino-producing decays of mesons,
  Hadron Absorber  absorber for non-decaying particles, and associated
                   radiation shielding

  Neutrino Beam    Measurement of flux and profiles of secondary beam and
  Monitoring       muons

  Survey,          Accurate determination of the neutrino beam centerline
  Alignment &      at Fermilab and Soudan. Accurate positioning of the
  Geodesy          neutrino beamline elements

  Beamline         Water, vacuum and gas
  Utilities        

  Controls, Cables Controls systems, cable specifications and
  & Interlocks     installation, interlocks methodology and locations
  ---------------- ------------------------------------------------------

**Table 1-1** Technical components of the NuMI beamline

  --------------- ------------------------ ------------------------------
  Downward slope                           58 mr (3.3°)
  of ν beam                                

  Proton                                   2.5 × 10^13^ p/1.9 sec
  intensity                                

  Spill length                             8 μsec

  Protons on                               2.5 × 10^20^
  target per year                          

  Target material                          Graphite

  Pion focusing                            Wide band, 2 horn

  Neutrino Energy                          
  Options                                  

  Baseline        Low Energy               1 - 3 GeV

  Option 1        Medium energy            3 - 8 GeV

  Option 2        High energy              8 -16 GeV

  Decay pipe                               1 m radius × 675 m long

  Downstream                               Ion chambers upstream of
  hadron                                   absorber
  monitoring                               

  Muon absorber                            240 m of dolomite

  Muon monitoring                          Ion chambers in absorber
                                           enclosure and alcoves in the
                                           dolomite shield
  --------------- ------------------------ ------------------------------

Table 1-2 Parameters for the NuMI beamline

# Performance and Operational Goals 

The Main Injector is a very high intensity proton accelerator that can
provide an adequate neutrino event rate even in a detector 735 km away.
Furthermore, the anticipated mode of operation of the Main Injector
during the next decade is well suited to the NuMI Project. The
accelerator must operate a significant fraction of the time to produce
antiprotons for $\overline{p} - p$ collisions in the Tevatron. However,
only one of six bunches are to be used for antiproton production, the
other five being available for stationary target experiments such as
MINOS. Furthermore, the Main Injector has adequate design margin and
scope for upgrades in key subsystems so there is a good possibility that
its intensity will increase with time and thus experiments with higher
statistics and better sensitivity will be possible in the future.

The production of the neutrino beam occurs in two stages. First the 120
GeV proton beam from the Main Injector is directed by single-turn
extraction into the NuMI beamline. In the NuMI beamline, the protons are
focused onto a segmented target, producing secondary mesons, both pions
and kaons. Because the neutrino beam must be aimed at the Soudan
Underground Laboratory, the proton beam is directed downward at 58 mrad
before it strikes the target. Subsequently, forward-going particles
(mesons) in the energy range of interest are focused and allowed to
decay, producing neutrinos. The focusing is performed by a set of two
magnetic horns. These devices are shaped in such a way that, when a
pulse of current passes through them, a magnetic field is generated
which focuses particles in the desired momentum range over a wide range
of production angles. The average meson energy is selected by adjusting
the locations of the second horn and target with respect to the first
horn. Thus, this "zoom" beam optics design allows the energy of the
meson beam (and therefore of the neutrino beam) to be varied during the
course of the experiment.

The particles selected by the focusing horns (mainly pions with a small
component of kaons and uninteracting protons) are then allowed to
propagate down an evacuated beam pipe (decay tunnel) 1 m in radius and
675 m long, placed in a tunnel, pointing downward towards Soudan. While
traversing the beam pipe, a fraction of mesons decay, yielding
forward-going neutrinos. By adjusting the energy of the parent meson
beam, a neutrino beam in the desired energy range can be obtained. As
mentioned above, this feature is crucial to our ability to
experimentally explore a wide range of possible oscillation parameters
and to minimize the errors associated with these measurements. A hadron
absorber is placed at the end of the decay pipe to remove the residual
flux of protons and mesons, followed by a set of beam monitoring
detectors.

The neutrino beam line has the following design objectives:

-   Potentially cover the energy range 1 to 20 GeV. This is accomplished
    by a hadron focusing system that can be optimized to 1-3 GeV, 3-8
    GeV or 8-20 GeV in neutrino energy.

-   Predict the neutrino energy spectrum in the MINOS far detector to 2
    or 3%, if neutrino oscillations are absent, given a measurement of
    the spectrum at the MINOS near detector.

-   Center the neutrino beam at the detectors and to keep the effect of
    mis-steering to less than 2% anywhere in the neutrino spectrum.

-   Long term reliability, stability and reparability such that the
    facility is usable for a minimum of 10 years while assuring
    personnel safety and allowing for future modifications and upgrades.

The integrated technical goals of the NuMI facility and MINOS experiment
are listed in Table 1-3 and 1-4. The commissioning goals are the
parameter values that must be achieved for approval to start operations
(Critical Decision 4) and are given in Table 1-3. The operational goals,
which are needed for the NuMI project to accomplish its scientific
objectives, are expected to be reached after several years of operation
and are given in Table 1-4. Although the NuMI Project will have
sensitivity to a wide range of parameter space to search for neutrino
oscillations, recent scientific results from Japan strongly indicate the
most promising area to search within this parameter space. Thus the
project begins in its "Low Energy" beam configuration. The commissioning
goals are to be met with cosmic rays and atmospheric neutrinos to
demonstrate the effectiveness of the far neutrino detector. Measurements
made with the beamline monitoring instrumentation assure that the
neutrino beam is aimed correctly at the MINOS far detector.

  ----------------------- -------------------- ---------------------------
  Parameter               Measurement          Commissioning Goal

  Cosmic ray muons        Near Detector data   Majority of the 153 Near
  detected in the MINOS   read out through DAQ Detector planes sensitive
  Near Detector           system               to muons

  Cosmic ray muons        Far Detector data    Majority of the 484 planes
  detected in each of the read out through DAQ of the Far Detector
  two MINOS Far Detector  system               sensitive to muons.
  Super Modules                                Atmospheric neutrinos
                                               detected in the Far
                                               Detector.

  Proton intensity in     Toroid (or           Greater than 1x10^12^ 120
  target hall             equivalent) beam     GeV protons/spill
                          intensity monitor at 
                          entrance to the      
                          Target Hall          

  Beam alignment          Transverse           Proton direction
                          distributions of the established to within 1 mr
                          proton beam and      of the known direction to
                          secondary beam.      Soudan.

  Near detector neutrino  Charged current      Observe neutrinos in the
  flux                    event rate in 15 ton Near Detector produced by
                          fiducial region      the NuMI beam
  ----------------------- -------------------- ---------------------------

**Table 1-3** NuMI Technical Commissioning Goals

+--------------------------+------------------+------------------------+
| Parameter                | Measurement      | Operational Goal       |
+--------------------------+------------------+------------------------+
| Proton intensity in      | Toroid (or       | 2.5 x10^13^/spill      |
| target hall              | equivalent) beam |                        |
|                          | intensity        | 2.5 x10^20^/year       |
|                          | monitor at       |                        |
|                          | entrance to the  |                        |
|                          | Target Hall      |                        |
+--------------------------+------------------+------------------------+
| Beam alignment           | Transverse       | Neutrino Beam centered |
|                          | distributions of | at Soudan to +/-0.2mr  |
|                          | the proton beam  |                        |
|                          | and secondary    |                        |
|                          | beam             |                        |
+--------------------------+------------------+------------------------+
| Near detector neutrino   | Charged current  | 1.2x10^-14^            |
| flux                     | event rate in 15 | events/proton          |
|                          | ton fiducial     |                        |
|                          | region           |                        |
+--------------------------+------------------+------------------------+
| Far detector neutrino    | Charged current  | 4x10^-18^              |
| flux\*                   | event rate       | events/proton          |
+--------------------------+------------------+------------------------+
| Muon momentum resolution | Curvature vs.    | 14%                    |
| ^+^                      | range in         |                        |
|                          | magnetic overlap |                        |
|                          | region           |                        |
+--------------------------+------------------+------------------------+
| Hadron energy resolution | Test beam        | ΔE/E = 70%/E^1/2^ + 8% |
| ^+^                      |                  |                        |
+--------------------------+------------------+------------------------+
| Detection efficiency for | Event length     | 90% with \<4% neutral  |
| charged current events   | distribution     | current contamination  |
| ^+^                      |                  |                        |
+--------------------------+------------------+------------------------+

\*Assuming 50% reduction from neutrino oscillations

+Applies to both near and far detectors

**Table 1-4** NuMI Operational Technical Goals

# Organization of This Report

This report is organized into five chapters with several appendices.
Chapter 1 is the Introduction. Chapter 2 is the overview description of
the NuMI beamline including neutrino beam fundamentals, neutrino
oscillation experiments, and conceptual design of neutrino beam. Chapter
3 summarizes the design parameters of the NuMI beam as well as the
design drivers and basis. Chapter 4 contains a description of the
technical component subsystems as well as design specifications.
Discussion and descriptions of the technical component subsystems are
organized to follow the Work Breakdown Structure (WBS) of the project.
Chapter 5 summarizes the radiation safety.

[WBS Organization]{.underline}

Chapter 4 is organized according to the Work Breakdown Structure (WBS)
that has been adopted for the NuMI Project. All technical components are
contained in WBS category 1.1. The third digit of the WBS describes the
component type. and serve to number the sections of chapter 4.