A Bunch Length Monitor for JLab 12 GeV Upgrade Page: 3 of 3
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Proceedings of PAC2013, Pasadena, CA USA
the energy between two angular frequencies rc1 and rc2 is
3.25 9/ e274 f
E = y 3j j Ks/s(x)dxdy (25)
360 8 r 3pEo y y
Since the repetition rate in JLAB is 500 MHz, power can
be estimated by assuming the form factor is a Gaussian dis-
tribution, multiplying eq.(24) by 3.25 and using equations
(1), (2) then the estimated calculations for the power dis-
tribution as a function of wavelength for different bunch
lengths is shown in fig (3).one so, it will have the same magnetic permeability. The
chamber elastic limit is measured under vacuum and found
to be 70 MPa which is much less than the elastic limit of
the stainless steel.
The four assemblies are mounted on a rotatable flange
with jacking screws to provide small angular correction as
shown in fig(5). The alignment laser assembly has a cageAlignment
Laser
Assembly.-- Laser
S01 p=100um
U a=200 um
3 0- j ' = 300 um
S10-6
-] _) F10
10-' 10-6 10- 10- 0.001 0.01 0.1
Lg() miris
Insertab
SL Mirror
SL 1
Periscope Alignment y Alignment
Assembly Socket Pin
Mount
Flexible
Coupling
Jiew port
ble Mirror 1.5" Stoke Air -Assembly Cylinder
"Spring loaded"Figure 5: Chamber with laser & SL assembly.
Figure 3: Power spectrum for different bunch lengths.
CONSTRUCTION OF THE CHAMBER
The old chamber and its component is shown in fig(4a)
while the new one is shown in fig(4b). The new chamber
is built with four additional ports, two of them are for the
laser alignment assembly and the Synchorotron light (SL)
assembly, while the other two is for the insertable mirror as-
sembly. The difference between the new and old line is that
the spool section is removed. The new chamber is made
from 316 stainless steal with the same thickness as the oldHigh Energy m
Iput
0R04 Dipole
Injector InputHigh Energy
Input
Alignment
Assembly0R04 Dipole
2412 1-000 1All-Metal Yao Lead
Valve Cavity Shield
Spool p )
Section Flange
1 All-Metal Vao Lead
V alive , Cavity ShieldSsM
AssemblyBellows p
FlangeFigure 4: Old and new chamber.
ISBN 978-3-95450-138-0
1384system with a laser diode to help in the alignment. The in-
sertable mirror assembly has a mirror in each one, one to
help in the laser alignment while the other is to receive the
synchorotron light and reflected upward to the RTI. Both
assemblies are attached to stroke air cylinder which is a
spring loaded to fail out in case losing air or electrical sig-
nals. Also, the chamber has a view port to make sure that
the initial laser alignment is on the right spot.
CONCLUSION
The chamber will be installed by the end of the year
and as the upgrade finishes, the RTI will be installed. The
measurements will be taken in the second phase of the up-
grade as JLAB will be operated for one cycle and the results
will be compared to the zero-phasing technique used in the
north linac.
REFERENCES
[1] D.Wang et.al., Physical Review E, vol.57, p.2283 (1998).
[2] R.Akre et.al., Proceedings of EPAC, 2002.
[3] G.Berden et.al., Physical Review Letters, vol.99, p.164801
(2007).
[4] B.Leissner et.al., Proceedings of PAC, 1999.
[5] P.Evtushenko et.al., Proceedings of AIP, 2006.
[6] J.Thangaraj et.al., Review of Scientific Instruments 83,
p.043302 (2012).
[7] D.Wang et.al., Appl. Phys. Lett. 70 (4), 27 January 1997.
[8] David Jackson, Classical Electromagnetism, 3"d edition.06 Accelerator Systems
T22 - Reliability, OperabilityTHPMA13
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Ahmad, Mahmoud Mohamad Ali; Freyberger, Arne P.; Gubeli, Joseph F. & Krafft, Geoffrey A. A Bunch Length Monitor for JLab 12 GeV Upgrade, article, December 1, 2013; Newport News, Virginia. (https://digital.library.unt.edu/ark:/67531/metadc869026/m1/3/: accessed May 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.