**4.2.8 Target/baffle Carrier Design**

**4.2.8.1 Carrier Definition**

"Module" refers to the heavy shielding module that supports beam
components below it, and has positioning motors mounted on top of it.
The target/baffle carrier is a frame mounted on shafts through the
target/baffle module. The module provides motion control of the target
transverse to the beam by moving the shafts vertically and horizontally.
The carrier supplies precision motion control of the target along the
beam. When maintenance is required that cannot be done in situ, the
entire module with carrier and components still mounted on it is moved
to the work cell. The module, carrier, target and baffle are shown **in
Figure 4.2-1** and **Figure 4.2-2**.

*Please refer to the engineering drawing set for up-to-date definitive
dimensions and layout.* The integration drawing for the modules,
carrier, and horn 1 is **8874.000-ME-363028**. The final carrier
drawings have not been made yet.

**Figure 4.2-** Modules in target hall
shielding.![](media/image1.png){width="5.986111111111111in"
height="2.9305555555555554in"} Target/baffle carrier mounted below
target/baffle module, with target and baffle extended into the low
energy position. Also visible are carriage cross beams, steel shielding,
horn 1 mounted below horn 1 module.

![](media/image2.wmf){width="5.99375in" height="6.285416666666666in"}

**Figure 4.2-****20** Target/baffle carrier with target and baffle
mounted. Target shown extended into the low energy neutrino beam
position

**4.2.8.2 Target/Baffle Carrier Functions and Requirements**

Target/Baffle Carrier must:

-   Remotely drive target into horn along beam axis after module is set
    in place: target casing extends 66.2 cm into horn, target carrier
    frame has 7.1 cm clearance to horn, thus minimum of 73.3 cm forward
    travel.

-   Provide target motion capability to 250 cm retracted from the
    standard low energy running position, to enable changing the energy
    tune of the neutrino beam.

-   Set position of target and baffle to 0.5 mm transversely, and 1 mm
    longitudinally along beam line.

-   Maintain position of target and baffle to 0.5 mm transversely and 1
    mm longitudinally under beam heating from 4x10^13^ protons / 1.87
    sec striking target; this includes other beam energy tunes in
    addition to the standard low energy beam position.

-   Provide the motion capability of the target and baffle utilities:
    target water supply line, target water return line, target vacuum
    line, two Budal target monitor electrical lines, 8 thermocouple
    electrical lines.

-   Maintain 1 inch clearance to target hall chase walls, in addition to
    the allowance for +/- 8 mm horizontal and +8 mm / -7.5 inch vertical
    motion of support shafts.

-   Provide a 2 cm radius "stay-clear" through the support structure
    that allows beam scans of downstream components when the
    target/baffle carrier is remotely lowered off beam axis (by \~ 7.5
    inch).

-   Survive radiation dose of up to 10^11^ rad/year for up to 10 years
    (except for the drive shaft end which is above the module).

-   Be short enough that it can be extracted through the target module
    carriage (199 inches) and inserted in the work cell (216 inches)
    with the target frozen in the extended position, or frozen with the
    baffle sticking out the back end in the target fully retracted
    position.

In addition, carrier will provide:

-   Four tooling balls for survey, located at beamline elevation, one on
    each side of the beamline at each module endwall, visible through
    holes in the endwall.

-   A pair of limit switches at each end of the travel of the
    target/baffle.

-   Rotary encoder on drive shaft at the top of the module to give
    remote readback of location of target along beamline.

-   Include baffling to direct part of the chase air stream to the
    target that is otherwise blocked by the target base and support
    tube. Airflow must also be maintained over the length of the baffle
    and the target.

-   Rust prevention coating of drive shaft and any other (non-stainless)
    steel parts.

Note secondary containment of radioactive water leaks is built into the
target pile design, and is not a carrier design consideration.

**4.2.8.3 Target Motion Capability**

###### Low Energy Target Insertion

For the Low Energy Beam, the target will extend 66 cm into the horn with
only 3 mm transverse clearance at the tip. The choice was made not to
mount the target on the horn itself for fear of vibration damage to the
target from horn pulsing. The target module will be set in place with
the target in a retracted position. After the target module is surveyed
into position, and the axis of the carrier aligned with the beamline
(and horn) axis using the module motor drives, the target will be
extended along the beam line into the horn using the carrier motor
drive.

###### Other Neutrino Energy Tunes

In NuMI-NOTE-BEAM-0783 \[ref. [^1]\], the case was made that by
extending the range of motion of the low energy target upstream one
obtains the capability to quickly and easily change the energy of the
neutrino beam. Such alternate energy tunes are labeled "semi-medium" and
"semi-high" energy beams, and produce decent rates and spectra, although
not quite the performance that can be obtained with optimized targets
and horn 2 positions for the alternate tunes.

When moving the target, one is taking the chance that it could become
stuck in some location. The target is in a high-radiation environment
(e.g. humidity can turn to nitric acid), and repairs to the carrier
mechanisms after being irradiated is mostly limited to replacement.
Proper choice of materials can help mitigate this. However, this is a
risk explicitly taken, and reinforces the need to have a complete spare
target/baffle/carrier unit at beam-turn-on.

[Extended target motion by relocating target module]{.underline}

The target carrier allows for 2.5 m of target motion without moving the
target module. The target can be moved even further upstream by moving
the target module, although this is not a trivial exercise. The current
baseline design allows space for one to move the target module 2 m
upstream by unstacking some shielding, using the crane to move the 20
ton module, restacking shielding, and then doing a survey to check the
final position. This would result in a total target range of 4.5 meters,
but the last 0.5 m or so may be precluded by interference between the
baffle and target hall upstream wall and beam pipe. (The standard high
energy target position was 3.65 m upstream of the low energy position,
and is reachable in this scheme.) The target/baffle carriage cross beams
which limit the upstream movement of the module can be seen in **Figure
4.2-21**. Three pieces of steel shielding required for this new position
are not in the baseline project, and would have to be acquired before
the move.

###### Restriction of motion by carriage, workcell

  ------------------------ ------------------------- ---------------------
  **Carrier frame**        **Fixed frame**           **160 in.**

                                                     

  **Moving components**    **Total moving            **315.97 cm = 124.40
                           components**              in.**

                           Baffle length             150 cm

                           Baffle to vertical Target 68 cm
                           fin                       

                           Target fin length         95.38 cm

                           Target casing beyond fin  2.59 cm

                                                     

  **Length normal          **Components inside       **160 in.**
  extraction**             frame**                   

                                                     

  **Total length L.E.      **Frame with target       **188.86 in.**
  position**               extended**                

                           Target extension          28.86 in.

                           Frame length              160 in

                                                     

  **Total length fully     **2.5 m upstream of       **193.97 in**
  retracted**              L.E.**                    

                           Baffle extension          33.97 in.

                           Frame length              160 in
  ------------------------ ------------------------- ---------------------

Table 4.2-10 Length of target/baffle/carrier unit in various
configurations.

The opening in the target carriage shielding is 199.389 inches. The work
cell is 216 inches long. These two openings set the maximum length of
the target/baffle carrier and range of motion. The module with
target/baffle possibly frozen in the fully extended or fully retracted
position must be able to navigate through these openings, with operators
controlling the crane by camera and remote control due to the high
residual radiation.

In the target extended downstream position, the length of carrier plus
target is 189 inches. With 250 cm of motion capability, with the baffle
extended out the upstream end, the baffle plus carrier is 194 inches
long. See also Figure 4.2-22.

**Figure 4.2-****23** (Rotated) target carrier side view. Target and
baffle are shown in both Low Energy Beam extended position, and in fully
retracted highest energy beam position.

![](media/image3.png){width="3.2375in" height="7.8in"}

**4.2.8.4 Target/baffle carrier hardware design**

###### Carrier mechanical design

The target and baffle frames have rollers that ride on aluminum rails,
as shown **in Figure 4.2-24**. The rails are at beam height, and are
supported by an aluminum tube space frame. Two hangers (sometimes
miscalled clamps) connect the space frame to the shafts (not shown in
the figure), which come through the module. The mass of the various
components is summarized in **Table 4.2-11**.

**Figure .2-**![](media/image4.png){width="5.99375in"
height="5.508333333333334in"} Target carrier end view.

  ------------------ ---------------------------------- ---------- -------
  Components                                                       215 lb

                     Target Assy.                       150 lb     

                     Baffle Assy.                       65 lb      

  Coils                                                            47 lb

                     One steel loop                     0.581 lb   

                     Water in loop                      0.194 lb   

                     3x22 steel loops                   38.3 lb    

                     2x22 water loops                   8.5 lb     

  Carriage Assy.                                                   598 lb

                     Frame Assy.                        231 lb     

                     Target baffle left support         120 lb     

                     Target baffle right support        110 lb     

                     Shaft support                      44 lb      

                     Coil support                       23 lb      

                     Drive system                       70 lb      

  Drive shaft loads                                                82 lb

                     Components on 0.058 slope          12 lb      

                     Rolling friction (0.05 coef.)      11 lb      

                     Coil contraction, max.             30 lb      

                     Friction coil on supports (0.61    29 lb      
                     coef.)                                        
  ------------------ ---------------------------------- ---------- -------

**Table 4.2-11** Approximate mass of carrier components, and loads.

The aluminum rails are coated with tungsten-disulfide to provide a tough
surface for the rollers to ride on.

The rollers are commercially available cam-followers, black oxide coated
steel in an aluminum housing. (These may be replaced with stainless
steel if we can locate a vendor). They will be run dry, i.e. without
grease. It is expected that the target location will only be changed a
few hundred times, so the number of cycles is relatively small.

The drive shaft is 1-inch diameter 17-4 PH heat-treated stainless steel.

###### Carrier thermal considerations

When running in the ME or HE locations, some of the target support
shafts and rails will be downstream of the target, and thus receive
substantial energy deposition from the secondary beam. MARS was used to
calculate the energy depositions \[ref. [^2], see Figure 5 for summary
of study\]. In order to maintain thermal position stability, several
measures are taken.

Water cooling is supplied to the downstream module-to-carrier hanger
(sometimes known as the clamp, in analogy to its use for horn 1), and
the lower part of the support shaft is made of low-expansion steel. The
water-cooled clamp design is copied from the horn 1 module design \[ref.
[^3]\]. The bearing between this clamp and the carrier is on
beam-centerline vertically. The clamp water cooling is not required for
low energy beam running. Thus its water loop is separate on the module
from the target water loop, so that failure in this system would not
require replacing the target for low energy running.

The carrier frame and rails are made of minimal volume to surface ratio
aluminum and are kept at larger radius to the beam centerline. For
initial design studies, a frame constructed of ¼ inch thick wall ¾ inch
square aluminum tubing was assumed. The beam-heating of the tubing
plateaus about 1 m downstream of the start of the target (**Figure
4.2-26**). At a radius of 25 cm from the beam, the energy deposition in
the aluminum is around 0.032 watts/gram. Assuming a heat transfer
coefficient of 10 w/m^2^K to the 18 deg C air flowing in the chase, the
asymptotic temperature calculated was 55 deg C, which is acceptable for
the frame. The final design uses thinner 1/8 inch wall 2 inch square
tubing, and thus should experience less than half the temperature rise.
The beam heating upstream of the target is negligible.

The drive shaft is placed at a radius of 40 cm from the beam-centerline.
At that radius and downstream of the target, it is estimated that its
temperature will be between 100degC and 150degC. The part that sets the
target location is upstream of the target, and will remain cool. The
downstream end of the shaft can be constrained transversely, but
allowance must be made for a 2 mm longitudinal expansion of the
downstream part when running higher energy tunes.

**Figure 4.2-**![](media/image5.png){width="5.99375in"
height="8.644444444444444in"} Summary from study of beam energy
deposition in carrier using MARS.

###### Carrier Frame Stiffness

Analysis of carrier support frame distortion has been carried out for
three positions of the target; fully extended, fully retracted, and
halfway in between. The vertical mis-alignment of points on the target
and baffle due to changes in the loading of the carrier frame was at
most about 0.2 mm.

During the assembly of the target on the carrier frame, the target will
be aligned such that the upstream and downstream ends of the target fin
are vertically on axis; because of the sag of the target tube due to
gravity, the middle of the target will be a fraction of a mm above the
beam axis.

The sag of the drive shaft is 5/16 inch when the target is in the fully
extended position.

###### Flexible utility lines

The 2.5 m travel of the target is accommodated by compressing a coil of
22 loops of pipe, 3/8" O.D. 0.028" wall stainless, total length 38 m per
line. Three lines are used: water supply, water return, vacuum. In the
LE position, the coil is unloaded. Fully retracted by the 2.5 m, the
coil force is of order 30 lbs. The drive shaft is kept under tension,
eliminating worry about buckling. (Putting the drive shaft in
compression might have forced use of a larger diameter shaft,
exacerbating cooling problems due to the larger volume to surface
ratio). The maximum stress on the water line is calculated to be 18 ksi,
which is below the yield stress with shear factor of 35 ksi x 0.577 = 20
ksi.

Radiation hard thermocouple cable is produced commercially, consisting
of a stainless steel sheath encapsulating a pair of wires in magnesium
oxide insulation. We will use this cable for all electrical routing on
the carrier. The flex necessary for the target motion will be obtained
in similar fashion to that for the utility lines, i.e. a coil that
expands or contracts, resting on an immobile support shaft. The voltage
standoff required is reasonably modest. The target tube may see a
voltage of order 50 Volts from the horn, since it follows the horn
voltage closely due to beam ionization of the air between the horn and
target tube. The Budal monitor may be run with a bias voltage of up to
75 volts, although a smaller bias (down to zero) can be used if
necessary.

###### Target Module Endwall Penetrations

The Horn 1 module upstream endwall has six penetrations for utilities,
as shown in **Figure 4.2-28**. Target module upstream and downstream
endwalls will copy this, with the assignments for usage shown in **Table
4.2-12**.

![](media/image6.png){width="5.986111111111111in"
height="1.5277777777777777in"}

**Figure 4.2-****29** Top view of Horn 1 module upstream endwall, which
will be copied for the target module. Utility penetrations include those
labeled clamp, outer, inner, and the two large holes to the right of
those labeled inner.

  ------------------------ ----------------------------------------------
  Upstream endwall         

  1                        Upstream Left Survey Port

  2                        Upstream Right Survey Port

  3                        Drive Shaft for 2.5 m motion

  4                        Target water supply

  5                        Target water return

  6                        Target vacuum/helium line

  Downstream endwall       

  1                        Downstream Left Survey Port

  2                        Downstream Right Survey Port

  3                        Clamp water supply

  4                        Clamp water return

  5                        Electrical feed through #1

  6                        Electrical feed through #2
  ------------------------ ----------------------------------------------

**Table 4.2-12** Allocation of target-module endwall utility
penetrations.

Each electrical feed through contains five two-pin plugs. Connections
are as show **in Table 4.2-13**, where the third baffle thermocouple
could be re-allocated if some other electrical connection is required.

  ------ -------------------------------- --------------------------------
  Plug   Pin 1                            Pin 2

  1      Target Budal horizontal fin      Shield for horizontal fin signal

  2      Target Budal vertical fin        Shield for vertical fin signal

  3      Carrier thermocouple 1           Carrier thermocouple 1

  4      Carrier thermocouple 2           Carrier thermocouple 2

  5      Baffle thermocouple 1            Baffle thermocouple 1

  6      Baffle thermocouple 2            Baffle thermocouple 2

  7      Baffle thermocouple 3 (or spare) Baffle thermocouple 3 (or spare)

  8      Wire from target vacuum jacket   Ground for limit switches

  9      U.S. limit switch 1              U.S. limit switch 2

  10     D.S. limit switch 1              D.S. limit switch 2
  ------ -------------------------------- --------------------------------

**Table 1.2-13** Target carrier electrical pin allocation.

# References

[^1]: [Proposal for Continuously-Variable Beam
    Energy](http://beamdocs.fnal.gov/cgi-bin/public/DocDB/RetrieveFile?docid=730),
    M. Kostin, S. Kopp, M. Messier, D. Harris, J. Hylen, A. Para,
    NuMI-NOTE-BEAM-0783, 10/17/01.

[^2]: Energy deposition in target support structure, R. Rameika, B.
    Lundberg, 3/02.

[^3]: Thermal Analysis of Clamp Using MARS Analysis Heat Generations,
    Bob Wands, 9/12/01.