Browsing by Author "Fan, TC"

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Magnetic field features of various magnetic circuits on the sextupole magnet
(1996-10-01)
Hwang, CS
;
Chang, CH
;
Fan, TC
;
Uen, TM
;
Tseng, PK
In this study, two adjacent sextants were partially cut from one side of a sextupole magnet in order to accommodate the electron beam bending chamber associated with a three x-ray beam dine chamber. The yoke cutting of these two sextants creates a different magnetic circuit which induces several forbidden fields. Meanwhile, the fundamental strength of this magnetic circuit is less than that of the normal on cut sextupole magnets in the storage ring. An induced forbidden field and the lessened sextupole strength originated from the saturation effect occurring at the magnet's yoke cutting side. Therefore, an extra closed-loop magnetic circuit is added across the two adjacent sextants to compensate for the yoke's smaller core area. This extra magnetic circuit can eliminate the saturation effect which induces asymmetric field behavior. It can also compensate for the lessened sextupole strength. In this work, the field distribution for various excitation currents related to the three magnetic circuits were measured. The field measurement results with various excitation currents tell us that the field saturation phenomena create the asymmetry field, forbidden field, and the lessened sextupole strength of the yoke cut magnetic circuit.
Performances and characteristics of a prototype symmetric hybrid adjustable phase undulator
(1997-11-11)
Hwang, CS
;
Chang, CH
;
Fan, TC
;
Lin, FY
;
Wang, C
In this work, we construct and measure a prototype symmetric Hybrid Adjustable Phase Undulator (HAPU) with nine poles to compare phase change and gap change in terms of their features and performances. HAPU can also provide the different characteristics between the pure and hybrid adjustable phase undulator. The HAPU has been installed in the Synchrotron Radiation Research Center (SRRC) storage ring to test the performance of the beam dynamics and photon flux behavior. A three-orthogonal Hall probe and a long-loop-coil measurement system are also implemented to take the field measurements. The multipole field and electron trajectory correction are made by shimming, the magic finger, and the active end pole coil corrector. After the field measurements, the vertical integral strength of HAPU is markedly smaller than that of the Hybrid Adjustable Gap Undulator (HAGU) and confirm that no obvious distinction arises between HAPU and HAGU in terms of the spectrum flux. The electron beam dynamic performance in the storage ring indicates that the vertical tune shift of HAPU is three times smaller than that of HAGU. Meanwhile, the energy dynamic tuning with the digital global feedback turned on, the photon position and flux in the bending chamber beam line is invariant. In addition, the injection efficiency remains unaffected at any phase position and the electron beam lifetime does not change when HAPU is in the dynamic tuning.
Photon spectrum characteristics and magnetic field performance of the prototype hybrid symmetry undulator magnet in SRRC
(1997-10-01)
Hwang, CS
;
Chang, CH
;
Lin, FY
;
Fan, TC
;
Yeh, S
A prototype Halbach hybrid magnet structure undulator with period of 10 cm was used to achieve a high magnetic field. A nearly sinusoidal magnetic field strength of 0.964 Tesla at 24 mm gap was achieved. The magnetic field was also designed and calculated using the magneto-static 3-D code of ''TOSCA''. According to those results, the field uniformity was better than 0.1% in the field rolloff range of x = +/-10 mm at 24 mm gap. The real field profile was measured to find the magnetic field behavior and the photon energy spectrum characteristics. In addition, field distributions obtained from the field measurement and simulation were used to calculate the photon spectrum characteristic. After the multipole and spectrum shimming, the good field region was controlled within 100 G.cm in the range of -2 cm less than or equal to x less than or equal to 2 cm to increase the dynamic aperture. A maximum phase error around 5.5 degrees was achieved and then maintained a high flux in the higher harmonic spectrum. The photon flux intensity is very close to the value of the ideal field simulation, which is about 10(15) photons/sec/100mA/0.1%BW. The energy range of the first harmonic ranges from 5.2 to 220 eV and the higher harmonic energy can reach 1 KeV. The electron trajectory deviation was controlled to within 5 mu m to maintain a constant optical axis and satisfy the beam dynamic requirements.
The construction of a 9-pole prototype for SRRC U-10 undulator
(1996-07-01)
Chang, CH
;
Chang, LH
;
Chen, HH
;
Fan, TC
;
Hwang, CS
A 9-pole undulator prototype with a magnetic period length of 10 cm was designed and constructed to examine the mechanical and magnetic field performance. The hybrid permanent magnet structure was optimized by using 2D ''PANDIRA'' and 3D ''TOSCA'' magnetostatic codes. A half period magnet model was also fabricated to verify the magnetic Period length field strength on-axis and the transverse field roll-off within 0.1 % in the good field region of +/- 10 mm at a minimum gap of 22 mm. The end pole configurations, as equipped with either two tunable permanent magnetic rotators or steering coil correctors were designed for minimizing the deviation of the magnetic field strength integrals. The magnet structures were mounted bn a 2 meter long C-frame support structure in which the gap could be moved in parallel and phase motion. The field characteristics, and measurement results between the adjustable gap undulator (AGO) and the hybrid adjustable phase undulator (APU) were also presented.