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LCLS Conceptual Design Report - Stanford Synchrotron Radiation ...

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L C L S C O N C E P T U A L D E S I G N R E P O R T<br />

Table 9.4 Thicknesses of boron carbide required for attenuation of 8 keV x-rays<br />

Linear attenuator Logarithmic attenuator<br />

Desired attenuation B4C thickness (mm) Desired attenuation B4C thickness (mm)<br />

1 0 10 -1 4.1<br />

0.9 0.2 10 -2 8.1<br />

0.8 0.4 10 -3 12.2<br />

0.7 0.6 10 -4 16.3<br />

0.6 0.9 10 -5 20.4<br />

0.5 1.2 10 -6 24.4<br />

0.4 1.6 10 -7 28.5<br />

0.3 2.1 10 -8 32.6<br />

0.2 2.8 10 -9 36.7<br />

0.1 4.1 10 -10 40.7<br />

Beam<br />

4 mm<br />

Linear attenuator<br />

Figure 9.8 A linear/log attenuator system<br />

Log attenuator<br />

4 mm<br />

B4C<br />

32.6 mm<br />

1 cm<br />

The attenuators will be fashioned from single plates of B4C milled in a staircase pattern to the<br />

thicknesses specified in Table 9.4 as shown in Figure 9.8. The linear and logarithmic attenuators<br />

will be mounted on separate translation stages allowing all combinations of linear and logarithmic<br />

attenuation to be applied.<br />

X - R A Y B E A M T R A N S P O R T A N D D I A G N O S T I C S ♦ 9-13

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