Abstract:A novel type of highly tunable permanent magnet (PM) based quadrupole has been designed by the ZEPTO collaboration. A prototype of the design (ZEPTO-Q1), intended to match the specification for the CLIC Drive Beam Decelerator, was built and magnetically measured at Daresbury Laboratory and CERN. The prototype utilises two pairs of PMs which move in opposite directions along a single vertical axis to produce a quadrupole gradient variable between 15 and 60 T/m. The prototype meets CLIC's challenging specificati… Show more
“…PMQs are more compact than electromagnets and can be made vacuum compatible, allowing them to be located close to the plasma source, within the same vacuum chamber. Figure 3 ZEPTO quadrupole 52 : an adjustable-strength permanent magnet. ( a ) A photo of the prototype high gradient ZEPTO quadrupole 53 .…”
Section: Methodsmentioning
confidence: 99%
“… ZEPTO quadrupole 52 : an adjustable-strength permanent magnet. ( a ) A photo of the prototype high gradient ZEPTO quadrupole 53 .…”
Section: Methodsmentioning
confidence: 99%
“…Therefore, we incorporate PMQs which have movable magnetic material that allows the strength to be adjusted without changing the position of the PMQ or the aperture size. We choose an adapted version of the ZEPTO 52 quadrupole design with an inscribed diameter of 6 mm, field gradient range of to and magnetic length of 100 mm. Adding a metallic seal coat 54 to the magnetic material and using vacuum grease on the movable parts will make the ZEPTO quadrupole design vacuum compatible.…”
Laser wakefield accelerators (LWFAs) can produce high-energy electron bunches in short distances. Successfully coupling these sources with undulators has the potential to form an LWFA-driven free-electron laser (FEL), providing high-intensity short-wavelength radiation. Electron bunches produced from LWFAs have a correlated distribution in longitudinal phase space: a chirp. However, both LWFAs and FELs have strict parameter requirements. The bunch chirp created using ideal LWFA parameters may not suit the FEL; for example, a chirp can reduce the high peak current required for free-electron lasing. We, therefore, design a flexible beamline that can accept either positively or negatively chirped LWFA bunches and adjust the chirp during transport to an undulator. We have used the accelerator design program MAD8 to design a beamline in stages, and to track particle bunches. The final beamline design can produce ambidirectional values of longitudinal dispersion ($$R_{56}$$
R
56
): we demonstrate values of + 0.20 mm, 0.00 mm and − 0.22 mm. Positive or negative values of $$R_{56}$$
R
56
apply a shear forward or backward in the longitudinal phase space of the electron bunch, which provides control of the bunch chirp. This chirp control during the bunch transport gives an additional free parameter and marks a new approach to matching future LWFA-driven FELs.
“…PMQs are more compact than electromagnets and can be made vacuum compatible, allowing them to be located close to the plasma source, within the same vacuum chamber. Figure 3 ZEPTO quadrupole 52 : an adjustable-strength permanent magnet. ( a ) A photo of the prototype high gradient ZEPTO quadrupole 53 .…”
Section: Methodsmentioning
confidence: 99%
“… ZEPTO quadrupole 52 : an adjustable-strength permanent magnet. ( a ) A photo of the prototype high gradient ZEPTO quadrupole 53 .…”
Section: Methodsmentioning
confidence: 99%
“…Therefore, we incorporate PMQs which have movable magnetic material that allows the strength to be adjusted without changing the position of the PMQ or the aperture size. We choose an adapted version of the ZEPTO 52 quadrupole design with an inscribed diameter of 6 mm, field gradient range of to and magnetic length of 100 mm. Adding a metallic seal coat 54 to the magnetic material and using vacuum grease on the movable parts will make the ZEPTO quadrupole design vacuum compatible.…”
Laser wakefield accelerators (LWFAs) can produce high-energy electron bunches in short distances. Successfully coupling these sources with undulators has the potential to form an LWFA-driven free-electron laser (FEL), providing high-intensity short-wavelength radiation. Electron bunches produced from LWFAs have a correlated distribution in longitudinal phase space: a chirp. However, both LWFAs and FELs have strict parameter requirements. The bunch chirp created using ideal LWFA parameters may not suit the FEL; for example, a chirp can reduce the high peak current required for free-electron lasing. We, therefore, design a flexible beamline that can accept either positively or negatively chirped LWFA bunches and adjust the chirp during transport to an undulator. We have used the accelerator design program MAD8 to design a beamline in stages, and to track particle bunches. The final beamline design can produce ambidirectional values of longitudinal dispersion ($$R_{56}$$
R
56
): we demonstrate values of + 0.20 mm, 0.00 mm and − 0.22 mm. Positive or negative values of $$R_{56}$$
R
56
apply a shear forward or backward in the longitudinal phase space of the electron bunch, which provides control of the bunch chirp. This chirp control during the bunch transport gives an additional free parameter and marks a new approach to matching future LWFA-driven FELs.
“…A promising avenue for further reducing the size of the internal quadrupoles is to make use of permanent-magnet technologies, as used in CERN's Linac 4 [7,8] and elsewhere [9][10][11][12]. This also removes the requirements for electrical power and control of the electromagnets, and complicated cooling systems, but at the expense of control of the magnetic field [13]. Once the permanent magnets are installed, the field pattern is fixed and cannot be adjusted.…”
Section: Introductionmentioning
confidence: 99%
“…When a beam is first switched on, the current will start from zero and then rise up to full operational beam current. For high intensity accelerators, the difference in space-charge forces from zero to full current is substantial, and controlling the beam over the full range of current using fixed permanent magnets is problematic [13]. For linacs that are designed to accelerate different species of ions, the difficulties are even greater, as the variation of field gradient required to control the beam for different ion species is an order of magnitude higher than the variation required to handle changes in beam current for a single species [14].…”
Magnets to be used for the internal quadrupoles of an interdigital H-mode drift tube linear accelerator (IH-DTL) using KONUS beam dynamics should be both compact in size and high in focusing field gradient. Permanent magnets are an attractive solution, but then the ability to adjust the field strength is lost. We investigated two different solutions to this problem: the first using external adjustable electromagnets; the second using internal adjustable permanent magnets. The first method moves the variability out of the resonant cavity, using adjustable electromagnet quadrupole doublets before entry into the IH-DTL to compensate for the lack of internal variability. We carried out optimization simulations with custom code that ran many instances of the LORASR beam dynamics simulation software, using different values of field strength for the external doublets. By optimizing the magnet settings for different values of input current, we were able to compensate for the space-charge forces involved in accelerating a high-intensity continuous-wave (CW) deuteron beam. Second, we designed some novel adjustable permanent-magnet quadrupoles to be used inside the cavity, which combine the advantages of small cross-section and variable field gradient. This allows much more control over the beam, and even other ion species with differing charge-to-mass ratios can be accommodated within the same accelerator design. We developed two adjustable permanent-magnet designs: one with an electromagnetic component, and the other with two concentric moving rings of Halbach-array quadrupoles.
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