24 May 2010
EMMA Injection Magnet Module Installation
A key milestone for the construction of EMMA was successfully achieved on Saturday 15th May, when the EMMA injection magnet module was craned into position in the EMMA ring.
Watch construction movie »
…read more below
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[toggle_item title=”EMMA Injection Magnet Module Installation”]A key milestone for the construction of EMMA was successfully achieved on Saturday 15th May, when the EMMA injection magnet module was craned into position in the EMMA ring. During the same day a 6th sector of the accelerator was also installed leaving just the extraction module to be installed.
The injection magnet module installation is significant, since is completes a long and complex process from accelerator physics beam simulations and magnetic design, through to multidisciplinary engineering design, manufacture, precise assembly and rigorous performance testing offline prior to installation in the ALICE accelerator hall. The achievement has been a complete in‐house project as commercial suppliers did not bid due to the technical complexity and risks involved.
The injection magnet system will steer single bunches of electrons at any energy from 10 to 20 MeV into the full acceptance of the EMMA ring, for each of eight different lattices to be studied on this proof of principle non‐scaling fixed field alternating gradient accelerator, that has a range of potential applications. Due to the very short straight section between the focussing quadrupoles in EMMA, the angle of injection is very large at 65°. These stringent space constraints, multiple energies and many lattices, make what is already a difficult task, very challenging.
The injection system consists of a septum magnet and two kicker magnets, in consecutive cells. To achieve the specifications, the septum has been designed for a peak field of 1 Tesla and it is able to translate and rotate to accommodate the various lattice configurations and energy range. In addition, the leakage field into the beam aperture must be extremely low so as not to impact on the circulating beam. Careful optimisation of the design predicted a leakage field of only 0.04% and this has been confirmed by magnet measurements. However, even this remarkably low field may not be low enough. As a result, it is planned to correct the small kick this field will give to the circulating beam using the ring magnets. The septum will be powered using a 25 μs long half sine wave current pulse at 7.5 kA. Figure 1 shows the septum before installation into its vacuum chamber. The septum is constructed from 760 high quality silicon steel laminations, 0.1 mm in thickness, with a 97% packing factor. To achieve the vacuum specification, all components were pre‐baked before assembly and the complete septum was further baked in vacuum by powering the pulsed magnet at 15 Hz repetition rate for an 18 hour soak test, where the temperature reached 120°C for 11 hours. This was sufficient to drive water content from the septum laminations and reach the required pressure of 1.2 x 10-7 mbar. Figure 2 shows a photograph of the septum in the vacuum chamber during motion control accuracy testing of the in‐vacuum bearing systems using a laser tracker and precision electronic level. The linear motion drives are repeatable to ± 3μm and level of the magnet is repeatable to 10μR.
Although the primary aim of the kickers is to steer the beam onto the correct orbit, they are also used to probe the horizontal acceptance of the accelerator. As they are in the ring, their field must be switched off very quickly before the beam returns about 55ns later. In addition, any subsequent ripples must be extremely low, to minimise the effect on later orbits. This is challenging and development work continues on a solid state power amplifier, employing a half sine wave voltage pulse, to produce the field, fast switching and optimised post pulse form. The kicker is a C shaped ferrite design as seen in figure 3, with a single turn conductor connected through the vacuum chamber with a coaxial feedthrough to minimise inductance. The kickers have been successfully tested in atmosphere and achieved the 0.007 Tm field strength specification at 28 kV. An in‐vacuum field probe attached to the kicker has also been implemented to obtain a clean and reliable pulse form diagnostic, to enable the pulsed power supply to be optimised in situ.
Work now focuses on the build and testing of the extraction module, which is a similar septum and 2 kicker magnet configuration required to extract the beam out of EMMA. The module is scheduled to be ready for installation by 17th June. In parallel, 4 sector commissioning of EMMA with electrons is scheduled to start in mid June and full ring commissioning in August.
Figure 1: Septum Magnet
Figure 1: Septum Magnet
Figure 3: Kicker Magnet
Figure 4: Injection magnet module installed in EMMA
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21 May 2010
Richard Carter Fest & NVEC
14 & 15 July 2010
10 May 2010
ICFA Newsletter No. 51
Swapan Chattopadhyay (Cockcroft Institute, UK) has completed the editing of ICFA BD Newsletter No. 51 (April 2010). …read more below
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Swapan Chattopadhyay (Cockcroft Institute, UK) has completed the editing of ICFA BD Newsletter No. 51 (April 2010). You can find it here ICFA Newsletter (pdf 10mb).
This issue has 251 pages. The theme is “Accelerator Science and Technology in the UK.” Swapan collected 29 excellent articles in this section. These articles give a comprehensive review of a variety of accelerator projects and activities in the UK, covering a wide spectrum including particle and nuclear physics, photon science, neutron science, test facilities and accelerator systems R&D, advanced accelerator R&D and new initiatives, applications to energy, health and security, and industrial engagement.
This issue has a report from a Joint ICFA-ICUIL Workshop on “High Power Laser Technology for Future Accelerators,” an announcement of the Fifth International Accelerator School for Linear Colliders, two recent doctoral theses abstracts (Stephen Brooks of Oxford U. and Jianjun Yang of Tsinghua U.) and three workshop announcements (ELOUD2010, BOD2010 and Cyclotrons2010).
Swapan edited a newsletter of excellent quality and great value to the accelerator community. On behalf of the Panel, I want to thank him for a job well done.
The next issue editor for No. 52 (August 2010) is Wolfram Fischer (BNL, USA). The deadline for submitting papers and announcements is July 15, 2010.[/toggle_item]
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