SCID Design

Consider three possible design approaches

1.  Use a scraper at minimum gap to fully mask 4K bore.

2.  Put 4K bore at minimum gap compatible with synchrotron power load
    associated with normal beam conditions.

3.  Put 20 - 50K bore at minimum gap compatible with synchrotron power
    load associated with normal beam conditions.

Difference between cold bore aperture and magnetic gap:

-   *dg* \~ 1 mm @ 4K.

-   *dg* \~ 3 mm @ 20 - 50K.

Synchrotron radiation sources:

+-----------------------------------+-----------------------------------+
| # Magnet                          | Distance to Straight Center \[m\] |
+-----------------------------------+-----------------------------------+
| Dipole                            | 5.13                              |
+-----------------------------------+-----------------------------------+
| Corrector 1                       | 3.94                              |
+-----------------------------------+-----------------------------------+
| Corrector 2                       | 2.84                              |
+-----------------------------------+-----------------------------------+

Simplified Source Model:

-   Source at center of magnet

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-   Hard edge field

    -   For *E~e~* = 1.9 GeV, *I* = 0.4 A:

![](media/image1.wmf)

![](media/image2.wmf)

> Fraction absorbed at aperture:
>
> ![](media/image3.wmf)

**Case 1**

Place scraper/mask at center of straight with 5mm gap. SCID is
downstream. *L* = 2m. Base layout on masking corrector 2, the closest
source.

![](media/image4.wmf){width="5.989583333333333in"
height="1.9472222222222222in"}

*a* = 8.5 mm

*g* = 9.5 mm

** = 23mm, *B~0~* = 1.5 T, *E~1~* = 240 eV

## Note that this is the basis for the previous solution considered. However we were using 8mm as the minimum allowed gap. 

## Case 2

Place 4K bore at minimum gap. Base layout on dipole, farthest source.
Place SCID at center of straight. Still use 5mm scraper to mask as much
as possible.

![](media/image5.wmf){width="5.989583333333333in"
height="1.9472222222222222in"}

Upstream photon masks allow 0.024 rad of dipole radiation fan to enter
the straight.

Total power, *P~T~* = 37W.

Power absorbed by scraper, *P~s~* = 0.64W.

Power absorbed at bore is a function of *a.*

  ----------------------------------- -----------------------------------
  ***a* \[mm\]**                      ***P~a~* \[W\]**

  5                                   1.8

  6                                   0.8

  7                                   0.2
  ----------------------------------- -----------------------------------

*a* = 7mm

g = 8mm

> a\) ** = 20mm, *B~0~* = 1.5T, *E~1~* = 350 eV
>
> Period doubling: ** = 40mm, *B~0~* = 1.5T, *E~1~* = 50 eV
>
> (*B~p~* \~ 1.7T)
>
> Unrestricted *B~p~* \~ 2.9T, *B~0~* \~ 2.5T, *E~1~* \~ 20 eV
>
> b\) ** = 22mm, *B~0~* = 1.6T, *E~1~* = 240 eV
>
> c\) ** = 23mm, *B~0~* = 1.5T, *E~1~* = 240 eV - same as Case 1

**Period Doubling:**

Normal configuration:

![](media/image6.wmf){width="5.989583333333333in"
height="0.48333333333333334in"}

Doubled configuration:

![](media/image7.wmf){width="5.989583333333333in"
height="0.7388888888888889in"}

Wind as two coils. Reverse polarity of one coil to double period.

**Case 3**

Place 20 - 50K bore at *a* = 5mm. Same layout as Case 2. Achieve same
result as Case 1, Case 2c.

*a* = 5.0 mm

*g* = 8.0 - 9.5 mm

** = 23mm, *B~0~* = 1.5 T, *E~1~* = 240 eV

Cryocooler for "warmer" bore has much higher capacity, \~20 -- 50W.

-   1.8W absorbed for nominal beam conditions is no problem.

-   Consider extreme mis-steer during accelerator physics. *I* = 0.04A.
    If all power entering straight (dipole and correctors) is deposited
    on bore, *P~a~* \< 5W. Still OK.

-   For extreme mis-steer at full current, *P~T~* \~ 50W. This would
    like cause a quench. This is extremely unlikely, may not be
    possible.

![](media/image8.png){width="6.0in" height="4.5in"}