# NuMI Low Energy Target

(in-line documentation)

## Serial number: 001

Date of Manufacture: 01/15/2003

1.  [Pertinent Process Information]{.underline}

The process of the construction of the target is described in the
document "NuMI Low Energy Target Specification", last revision from
01/31/2003. The conformance certification of the each constructed part
to the requirements of appropriate drawing was carried out by
engineering inspection divisions of the IHEP, Protvino and IPPE, Obninsk
workshops.

To provide the nonflatness tolerance of the target core equal to 0.2 mm,
as specified in the drawing 7589-01-50-00, cross section B-B, the
special soldering furnace for the assembly of the target core was built
(Figure 1).

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  ![](media/image1.wmf){width="5.501388888888889in"
  height="5.120138888888889in"}

  Figure 1. The assembly of the target core in the soldering furnace
  during the process of soldering.
  -----------------------------------------------------------------------

The base plate and holes for rods were machined by the coordinate boring
machine (the accuracy to within 10 μm). Target segments are placed on
the precise smooth surface of the base plate machined by the grinding
machine. The transverse size of this surface is a few millimeters less
than the height of the graphite segment. It provides sliding of target
segments during the soldering process. The assembly of cooling pipes and
target segments are pressed to the rods by springs, uniformly spaced
along the target core length. Soldering of this assembly is carried out
in the argon environment. The low heating rate equal to 10°C/5 min
minimizes the warpage of the base plate, as well as that of the target
core assembly. To prevent the warpage of the target core with soldered
cooling pipes during cooling process the steel weight with precise
grinding surface is placed on the graphite core as it is shown in Figure
2.

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  ![](media/image2.wmf){width="3.522222222222222in"
  height="2.5340277777777778in"}

  Figure 2. The assembly for cooling process of the soldered target core.
  -----------------------------------------------------------------------

2.  [Required Mechanical Dimensions]{.underline}

Measured dimensions compared to the specified in appropriate Engineering
Drawings are given in Table 1.

  ----------------------------------- ----------------- -----------------
  Dimension                           Specified, mm     Measured, mm

  The length of the graphite core     953.8 ~--2.3~     952 ± 0.1

  The height clearance of the target  27.4              27.4 ± 0.01
  core with soldered cooling pipes                      

  The distance between the downstream 32.2              34±0.1
  plane of mounting flange and the                      
  first target segment                                  
  ----------------------------------- ----------------- -----------------

Table 1. Measured mechanical dimensions compared to the specified in
appropriate Engineering Drawings.

The measured position of the cross with respect to the center of the
compensation ring of the beryllium window is shown in Figure 3.
Measurements were carried out with help of the theodolite−level.

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  ![](media/image3.wmf){width="2.920138888888889in"
  height="2.109027777777778in"}

  Figure 3. Measured position (mm) of the cross with respect to the ring
  center.
  -----------------------------------------------------------------------

3.  [Required Electric Check]{.underline}

Required electric check involving measurements of resistances between
different parts of the target at 100 V, were carried out by the E6−13
teraohm-meter. Results of measurements are given in Table 2.

+---------------------------------------------------+------------------+
| The target core and ground (mounting flange)      | \>10^11^         |
+---------------------------------------------------+------------------+
| ### The target core and target casing             | 1×10^10^         |
+---------------------------------------------------+------------------+
| The vertical monitoring graphite plate and ground | 3×10^10^         |
+---------------------------------------------------+------------------+

Table 2. Measured resistances (Ohm) between different parts of the
target.

4.  [Required Vaccum Test]{.underline}

Vacuum tests were carried out at vacuum 10^--3^ Torr by the PTI − 10
helium leak detector with sensitivity of 10^--10^ Torr×l/s. Three types
of vacuum tests were carried out at the stage of the construction of the
target as specified in appropriate Engineering Drawings and "NuMI Low
Energy Target Specification":

-   each of welded or brazed joints. In case of the leakage the joint is
    repaired until the vacuum tightness of the joint was reached and the
    leak reduced below 10^--7^ Torr×l/s;

-   each of separate assembly or sub-assembly. No leakage was detected;

-   the final assembly of the target. No leakage was detected.

5.  [Required Hydraulic Tests]{.underline}

Two types of hydraulic tests of the target cooling system were carried
out at the stage of the construction of the target as specified in
appropriate Engineering Drawings and "NuMI Low Energy Target
Specification":

-   the static test at the water pressure equal to 0.3 MPa during 30
    min. No leakage was detected;

-   the test of the water flow rate at a pressure drop equal to 0.0981
    MPa. As measurements showed the water flow rate at this pressure
    drop was equal to 3.5^+0.2^ l/min.