Dr. R. Geller first proposed the concept of Electron Cyclotron Resonance in 1965 first time. A significant step forward occurred when R. Geller and his co-researcher crew transformed a mirror device, CIRCE, right into an adequate ion supply in 1974 named super-MAHIOS. To stabilize the plasma in opposition to the magnetohydrodynamic instabilities, they used a hexapole field together with a solenoid magnetic mirror field. It additionally provided a resonant area in the plasma chamber inside the closed ellipsoidal shape and assisted the electrons to be heated by the ECRH (Electron Cyclotron Resonance Heating) process. Several versions of this device had been tested throughout the last decade, but its primary features remained identical. Infect all modern-day ECR systems for high charge state are primarily based on the magnetic field design of super-MAFIOS. For the production of sextupole fields, super-MAFIOS have required a heavy electric power delivery of approximately 3MW. It is far because of the vast copper coils used to produce the sextuple area in the ECR system. To lower the intake of high electric powered power, one approach was to use permanent magnets to construct the magnetic field for the ion source on the grounds that Samarium-cobalt (Sm-Co) magnets were reachable on time. It changed into seemed to be impractical because super-MAFIOS is considered a perfect and any form of alternate at that time.
Once again, R. Geller and his co-researcher group have initiated this alteration, resulting in a new magnetic field configured with permanent magnets assist. A new sextupole field came into existence along with the miniaturized version of super-MAFIOS, later referred to as MINIMAFIOS. The use of permeant magnets reduced the diameter of the ECR chamber from 30 cm to 7 cm and the length reduced from 100 mm to 30 cm. comparable terminology was followed within the improvement of various ECR ion sources working at specific frequency spectrums. 2.45 GHz is the only lower end of the microwave frequency, and ECR ion sources based on the 2.45 GHz frequency spectrum have fast development, especially for their uses in the production of single and moderately charged states.
The design of the magnetic field profile has one of the measured factors here, the improvement of ion source based totally on 2.45 GHz microwave frequency. At the beginning of 1990, the Lawrence Berkeley Laboratory proposed a revolutionary layout of advanced ECR ion sources. This device used a hexapole structure at the injector side to achieve a radial get right of entry to the hollow plasma space. The axial magnetic field value reaches approximately 1T due to iron plates located at the discharge place; a mirror ratio is achieved at approximately 2.5, which was relatively high compared to the availably of the various system at that time [1]. The ECR ion source design by means of M. Leihr et al. used a new kind of magnetic discipline that became generated through permanent magnets only. To design a magnetic field profile, they have been used eighteen permanent magnets in three rings; each of the rings carried out six magnets. Those magnetic structural arrangements were beneficial in generating a dense and stable ECR plasma within the plasma cavity [2].
In 1991, k. Amemiya et al. did the primary reported work on the ECR ion source, emphasizing the 2.45 GHz system. They also used a design that used a single-stage plasma cavity instead of the standard-stage plasma source used till then. They used types of magnets for magnet assembly solenoid electromagnets and octopole permanent (Samarium-Cobalt) magnets superposed with each other [3]. S. Shibuya et al. performed a series of experiments with specific own novel improvements inside the magnetic field design in 1996 and 1997. Rings produce the mirror field; each of them had an outer and internal diameter of 13.5 cm and 10 cm, respectively and a thickness of approximately 3 cm. Their experimental work used NdFeB magnets; at the injection side, maximum magnetic area strength reached about 2.2 kG, and at the extraction site, this reached approximately 1.8 kG at the beam axis [4].
Similar work wholly based on permanent magnetic ring shape is executed by means of R. Trassl et al. in 1997; they used a magnetic field generated via one axially and radially magnetized rings to create a mirror field for axial confinement plasma within the ECR cavity. Their experiment found that at 8.85 GHz, satisfactory outcomes for such magnetic field configuration occur [5]. A Halbach - type hexapole with a radial magnetic area strength of 0.94 T around the inner partitions of the plasma cavity become used [6]. It was some other system that used all permanent magnets manufactured from NdFeB. In 2000, H. W. Zhao et al. published a review of the development of ECR ion resources, where they described current systems being developed at that time. Nearly all of the ECR systems developed had their Magnetic Fields mainly produced by a set of permanent ring magnets made up of NdFeB.
Moreover, those structures possessed three coils, A, B and C, which were used to change their Magnetic field Distribution. The combination of the electromagnet and the permanent magnet improved several ECR ion sources based totally on 2.45 GHz microwave frequency [7]. Few of these systems are mentioned inside the above section. These sources are commonly known for the production of moderate charge states. However, if we discuss the single charge state, there is a need to vary the magnetic field profile. Based on a 2.45 GHz ECRSIS system, a flat resonance field is needed at 875 Gauss. This magnetic field profile is without difficulty accomplished with the electromagnets and from permanent magnets; a few ECRIS based totally on those magnetic fields are mentioned below.
A high current proton ion source based on 2.45 GHz was designed by S.K Jain et al. in 2001. Their design comprised three electromagnetic coils to achieve the 100 mm axial magnetic field inside the ECR plasma cavity. Their design for the axial magnetic field also facilitates them to study off-resonance at the different power supplies to the electromagnet [8]. To achieve a high beam current and low emittance point of view, E. Tojyo et al. group performed similar work in 2002. To achieve an axial magnetic field profile, they used three rings of NdFeB permanent magnets in their system. Their permanent magnet-based design produced approximately 80 mm axial magnetic field profile inside the ECR plasma cavity [9].

Figure 1. (a) A design of 2.45 GHz ECR ion source along with three permanent magnetic ring structures. (b)Axial magnetic field profile for the three permanent magnetic ring structures. Reproduced from [9], with permission of the American Institute of Physics.
The use of permanent magnetic rings to designing axial magnetic field profiles also reduces the stray field around the extraction side; the system layout by S.X. Peng et al. is one instance of these types of structures. They used permanent magnetic rings and observed an about 60 mm axial magnetic field profile [10]. To achieve a higher plasma profile closer to the extraction site, O. Daniel Cortázar and his research group in 2012 designed a new system. Their design uses electromagnetic coils and achieves an axial magnetic field profile up to a length of 96 mm [11]. Similar work is also performed by S. K. Jain et al., with the help of three electromagnets in 2013. They obtained a flat axial magnetic field profile having length approximate 70mm to extract proton current in high-intensity light ion sources [12].

Figure 2. (i) View of the plasma chamber and main subsystems, (a) Plasma chamber, (b) MW impedance adaptor, (c) Coil pancakes, (d) Pressure gauge inlet, (e) Diagnostic port. (ii) Z-axis axial magnetic field profile at different power inputs. Reproduced from [11], with permission of the IEEE Nuclear and Plasma Sciences Society.
Inter-university accelerator center, Delhi also designed a compact permanent magnet-based 2.45 GHz ECRIS system using NdFeB magnets in 2014. in their design, the axial magnetic field profile is based on two permanent magnetic rings. These magnetic rings comprise wedge-shaped magnets having pole tips approximately 1T. The resulting magnetic axial field profile gets approximately 60 to 65 mm by adjusting permanent magnetic rings' center to center distance [13].

Figure 4. (a): View the microwave ion source coupled with the microwave and extraction systems. (b): Measured axial magnetic field generated by two permanent magnet rings. Reproduced from [13], with permission of the American Institute of Physics.
Most research groups develop ECR ion resources to attain lower emittance and better current. They are looking to generate a denser plasma profile within the ECR plasma cavity to accomplish this. To get denser axial ECR plasma Central University of Punjab department of Physics researcher group designed a new 2.45 GHz ECRIS system in 2021.

Figure 5. (a): Axial magnetic field variation concerning the center to the center gap between the permanent magnetic rings, keeping one ring fixed at the injection site. (b): Cross-sectional view of the magnetic field at a "center to center" gap of 155 mm. Reproduced from [14], with permission of the American Institute of Physics.
Their axial magnetic field profile is based on permanent magnetic ring arrangements. They designed a permanent magnetic ring arrangement through which it is possible to tune the axial magnetic field up to some extent by varying the gap between the magnetic rings on the ECR plasma cavity [14].
If seen here, plasma formation in the ECR ion source starts from the middle of the ECR cavity; after that, it spreads out toward the injection and extraction side of the ECR cavity. This formation pattern of ECR plasma is maintained inside the ECR plasma cavity. As a result, it is challenging to preserve the uniformity of ECR plasma inside the ECR plasma cavity. This problem is overcome with the help of electromagnets. A flat axial magnetic field profile is generated inside the ECR plasma cavity, and uniformity of ECR plasma is maintained throughout the axial distance of the plasma cavity. Therefore, we have left with a few choices here to generate the axial magnetic field profile (i) Electromagnets-Electromagnets, (ii) Electromagnet-Permanent magnets, (iii) Permanent Magnets-Permanent magnet. The choice of an electromagnets-based system or, along with permanent magnets, invites lots of power consumption. It is not easy to achieve a long-range axial magnetic field profile if we only go with permanent magnetic rings. We need a heavier and highly pole tip value of magnetic rings or multiple magnetic rings to achieve it. At the same time, it also leads to the bulky formation of the ECR system. Therefore, we need a system that resolves this problem and produces the uniform ECR plasma and long range axial magnetic field profile by avoiding the electromagnets.
Detailed Drwaings:

First Iron module

Figure 6: Detailed information of First Iron module structure which is used at the injection site within the ridge section adjacent the rectangular microwave window for long-range axial magnetic field profile for 2.45 GHz ECRIS.

Second Iron module

Figure 7: Detailed information of Second Iron module structure which is used at the extraction site within the two parts of plasma electrodes for long-range axial magnetic field profile for 2.45 GHz ECRIS.

The first part of Plasma Electrode

Figure 8: Detailed information of mechanical design features of First part of plasma electrode for 2.45 GHz ECRIS.

Second part of Plasma Electrode

Figure 9: Detailed information of mechanical design features of Second part of plasma electrode for 2.45 GHz ECRIS.

Prototype design for ECRIS to define the Positioning of both Iron modules within ECRIS

Figure 10: The positioning of the 1st & 2nd iron module inside the prototype ECRIS based on 2.45 GHz microwave frequency.

Description of Technical details
Details Description of the First Iron module (Figure 6):
In Figure 6, the first part of the iron-based mechanical assembly arrangement initiates a long-range axial magnetic field from the injection site. There are two stages in the mechanical design of the first iron module; here, the first step is an inclined plane with lengths of 7.12 mm, height 1 mm, and width 30 mm, respectively. The height of the second stage is 1.57 mm, and the width is 16 mm. The length of both the steps is kept equal to the width of the permanent magnetic ring, which is 35 mm. As mentioned earlier, a pair of dimensions are used as the first iron module; the full detailed description of all physical dimensions and mechanical view of the first iron module is shown in Figure 6, respectively.
Details description of Second iron module (Figure 7):
In figure 7, the second part of the iron-based mechanical structural arrangement, which initiates the long-range axial magnetic field from the extraction site. The second iron module is a combination of two iron frustum shapes, each frustum shape having a length of 17.5 mm. The small circular area at both frustum ends has a radius is 10.50 mm. The overall length of the combined mechanical structure is 35 mm, equal to the width of the circular permanent magnetic ring structure. A cut 8 mm wide and 1 mm deep is made at the joint of both the frustums. A hollow circular smooth hole is drilled along the entire length of the mechanical design, having a radius of 8 mm. Finally, a mechanical design for the second iron module is devised to have a flat-shaped axial magnetic field from the extraction site. All of the physical dimensions and mechanical design views for the second iron module at different viewing angles are shown in figure 7.

Details description of First part of Plasma electrode (Figure 8):
The complete design of the plasma electrode inside the ECR plasma cavity is divided into two parts (1st part & 2nd part of plasma electrode). The first part is designed so that the frustum part of the second iron module can be contained within the first part of the plasma electrode, as shown in the cross-sectional view in figure 8. The first part of the plasma electrode is cylindrical with a radius of 47.5 mm. A screw tightening system in the first part of the plasma cavity is adjusted to be easily fixed along the inner wall of the ECR plasma cavity. A small hole with a radius of 2 mm is oriented in the center of the plasma electrodes to extract the ion beam from them. Full details of all physical dimensions (mm) for the first part of the plasma electrode at different sides are shown in Figure 8.

Details description of Second part of Plasma electrode (Figure 9):
As mentioned earlier, the plasma electrode is designed in two parts. The first part is described in figure 8 description part. The second part of the plasma electrode is made into two arc-shaped structures. The shape of both the arcs is designed to be easily joined with the first part of the plasma electrode with the help of a screw tightening system. The internal design mechanism for the second part of the plasma electrode is such that it effectively maintains a firm grip on the flat cut section of the second iron module. In addition, the other frustum part of the iron module is also conveniently located within the second part of the plasma electrode. The second part of the plasma electrode itself maintains the position of the second iron module at a fixed position in the center of the second permanent magnetic ring structure. Full details of all physical dimensions (mm) for the second part of the plasma electrode at different sides are shown in Figure 9.
Details description of positioning of both iron modules within the ECRIS (Figure 10):
A prototype system has been designed to adjust both mechanically designed iron modules inside the ECRIS system. The position of these iron modules is shown by fixing them at a desirable location in this prototype design. So that it does not create any impedance for microwave coupling for 2.45 GHz ECRIS systems, and at the same time maintains the long-range axial magnetic field profile inside the ECR plasma cavity.

Position of First Iron module (Figure 10):
The first iron module is also made in two parts; The first part of the iron module is easily fitted to the upper part of the ridge section by drilling the corresponding rectangular section adjacent to the rectangular microwave window. Similarly, the second part of the first iron module is easily accommodated in the ridge section's lower part adjacent to the rectangular microwave window. Since the first iron module is within the ridge section, it will not cause any disturbance to microwave coupling or mode formation inside the respective ECR plasma cavity. Also, the position of the first iron module will be conveniently in the center of the first permanent magnetic ring assembly. A cross-sectional view of the ECR ion source with the first iron module settlement inside the waveguide section is shown in Figure 10.

Position of Second Iron module (Figure 10):
The second iron module is located in two parts of the plasma electrode. The adjustment of these parts of the plasma electrode has already been done in the detailed discussion in Figure 8 and Figure 9. The second iron module is also located at the center of the second permanent magnetic ring, similar to the first iron module. Since it is located on the extraction site, it will also not cause any disturbance to the microwave coupling process. The second iron module is designed to have a spherical internal shape so that there is no deflection of the ion beam during the extraction process from the plasma electrode. A cross-sectional view of the ECR ion source with both halves of the plasma electrode attached to the second iron module is shown in Figure 10

Description of Simulation details

Figure 11: A complete step-by-step information for assembly of magnetic ring formation for 2.45 GHz ECRIS system.
Details: A fairly generalized assembly based on permanent magnetic rings for a 2.45 GHz-based ECRIS system is shown in Figure 11. A total of 12 arc segments have been used to create the permanent magnetic ring structured formation. Each arc-shaped magnets have an inner and outer radius, and widths of 68 mm, 93 mm and 35 mm are used, as shown in Fig. 11(a). The first magnetic ring has the magnetization direction radially inwards, and the second magnetic ring has the magnetization direction radially outwards, as shown in Figures 11(b) and 11(c). A non-magnetic material (stainless steel) brings the magnetic arcs together in a circular ring. In conjunction with steel casings, magnetic rings have inner, outer radii and emerge in widths of 65 mm, 96 mm and 41 mm, as shown in Fig. 11(d) and 11(e). These radial magnetic rings are separated at a distance of 142 mm from center to center with the help of a ring holder, threaded rod and tighten stud system, as shown in Fig. 11(f)
A comparative axial magnetic field profile is simulated for two permanent magnetic ring assemblies. The first assembly of a permanent magnetic ring has been simulated without using any iron modules. In contrast, the second permanent ring assembly is simulated with the newly invented iron module. Same amplitude and magnetization directions are used in both the magnetic ring assemblies. Each magnetic ring consists of six arc-shaped permanent magnets having inner-outer radii and widths of 68 and 93 mm and 35 mm, respectively. The magnetization direction of the first ring is radial inward and radial outward for the second permanent magnetic ring. Simulations were carried out for the first pair of ring assemblies with a pole tip magnetic field of approximately 1065 G in each permanent arc form magnets. The resulting axial magnetic field profile is shown in Fig. 12(c).

Figure 12: A resultant axial magnetic field profile for the two magnetic ring structured arc magnets for a 2.45 GHz ECRIS system.
On the other hand, the second permanent magnetic ring assembly is simulated with the newly invented design of two iron modules located in the center of each magnetic ring. The magnet produces a pole tip magnetic field of about 0979 G in each permanent arc. The resulting output axial magnetic field profile for the second magnetic ring assembly is shown in Figure 9(c). Complete simulation is carried out in a Computer simulation technique software program (CST) in magnetic subject solver. The simulation outcome shows that the use of both magnetic ring pairs shows the axial magnetic subject profile inner the ECR plasma cavity. However, if the result of the second pair is observed, the second pair of rings produced the double axial ECR sector interior the ECR plasma cavity. We brought exceptional iron structures internal to the magnetic ring centre’s in the second pair of ring assembly.

Figure 9: A resultant axial magnetic field profile for the two magnetic ring structured arc magnets along with two iron module structures for a 2.45 GHz ECRIS system.
As a result, the ensuing axial subject profile increases inner the ECR plasma cavity. These two distinct iron constructions are brought to fulfil the circumstance of microwave coupling internal to the ECR Cavity. Suppose we use a similar iron structure at the center of both magnetic ring structures: the magnetic lies toward the injection site. In that case, the round iron ring shape can change the impedance of the ridge section which is adjacent to the rectangular microwave window, as a result of which microwave coupling result for the 2.45 GHz ECR cavity can be disturbed. Therefore, to avoid these disturbances, a flat-shaped iron section is used at the injection aspect inside the Ridge waveguide structure; a round section is used at the extraction aspect interior the plasma electrode. The stability of axial magnetic field profile from injection site to extraction site is shown in table 1.
Table 1: Standard deviation of axial magnetic field profile from injection site to extraction site.
Mean Standard Deviation Sum Minimum Median Maximum
0.0875 7.7157E-5 7.17508 0.08737 0.0875 0.0877

In conjunction with a better axial field profile, it is also found that the better awareness of axial magnetic subject profile is determined to be focused at the axial ECR zone. If we followed each of the above axial area profiles, the step interval in each magnetic subject profile is selected identical. The axial subject profile, which accommodates the iron ring structure, suggests that better concentrations are shaped at 875 Gauss than the relaxation of the location wherein is extensively less dense magnetic discipline profile is created. An iron ring shape within the ECR magnetic earrings may generate higher and long-variety concertation of axial plasma. Figure 10: A resultant axial magnetic field profile for the two magnetic ring structured arc magnets along with two iron module structures for a 2.45 GHz ECRIS system with an increase in remanence (Br) values.
As per simulated outcomes of electromagnets reported earlier [10-11], as we increase the power input for the electromagnet case, we can achieve the higher-order resonance zone for higher frequency order. Similar work is also performed for the present design here. Instead of power input, the Remanance (Br) value is increased for each arc magnet of the ring. The resultant magnetic field profile also behaves the same as per electromagnetic field profile, as shown in figure 10 for the different “Br” input values for each magnetic arc inside the magnetic ring.
The present axial magnetic flux profile is not limited to the prevailing rigid shape. Still, if we would like further growth in the axial magnetic flux profile therein case, we would like to play with the outer radius of the permanent magnetic arc structure and a similar iron structure already in use. This selection of present innovation enables obtaining an axial magnetic flux profile in the ECR plasma hollow space. The further long rang axial magnetic flux profile and variant inside the outer radius are proven underneath.

Therefore, the present invention leads to the compactness of the 2.45 GHz ECR system, making it a readily available facility for axial resonance plasma studies. In addition, replacement options for electromagnets for 2.45 GHz microwave systems have been designed for ion beam and plasma diagnosis facility points.

References
1. Xie, Zuqi, et al. "Enhanced ECR ion source performance with an electron gun." Review of scientific instruments 62.3 (1991): 775-778.

2. Liehr, M., et al. "A low power 2.45 GHz ECR ion source for multiply charged ions." Review of scientific instruments 63.4 (1992): 2541-2543.

3. Amemiya, K., K. Tokiguchi, and N. Sakudo. "Production of milliampere class mass-separated multiply charged ion beam." Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 9.2 (1991): 307-311.

4. Shibuya, S., et al. "Beam tests of a compact 2.45 GHz electron cyclotron resonance ion source." Review of scientific instruments 67.3 (1996): 1171-1173.

5. Trassl, R., et al. "Characterization and recent modifications of a compact 10 GHz electron cyclotron resonance (ECR) ion source for atomic physics experiments." Physica Scripta 1997.T73 (1997): 380.

6. Halbach, Klaus. "Design of permanent multipole magnets with oriented rare earth cobalt material." Nuclear instruments and methods 169.1 (1980): 1-10.

7. Zhao, H. W., et al. "Development of ECR ion sources in China." Review of Scientific Instruments 71.2 (2000): 646-650.

8. Jain, S. K., Akhilesh Jain, and P. R. Hannurkar. "High current microwave proton ion source." (2001).

9. Tojyo, E., et al. "A compact 2.45 GHz ECR ion source with permanent magnets for material science." Review of scientific instruments 73.2 (2002): 586-588.

10. Peng, S. X., et al. "Status of the high current permanent magnet 2.45 GHz ECR ion source at Peking University." Proceedings of ECRIS10 (2010): 102-104.

11. Cortázar, O. Daniel, Ana Megía-Macías, and Alvaro Vizcaíno-de-Julián. "Experimental study of breakdown time in a pulsed 2.45-GHz ECR hydrogen plasma reactor." IEEE transactions on plasma science 40.12 (2012): 3409-3419.

12. Jain, S. K., et al. "Characterization of proton beam emission from an electron cyclotron resonance ion source." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 708 (2013): 51-55.

We claims

1. The electromagnet for the 2.45 GHz ECRIS system is a cost-effective and power-saving alternative design capable of producing a long-range axial magnetic field profile.

2. An improved flat shape axial magnetic field profile has been obtained from a permanent magnetic ring by using a newly invented iron module design for the ECR ion source. The result is promising, generating a flat shape axial magnetic field profile from the injection side to the extraction site for a 2.45 GHz ECR ion source.

3. The newly designed iron modules and permanent magnetic rings can produce an almost double axial magnetic field profile compared to a conventional permanent magnetic ring based on a 2.45 GHz ECRIS system.

4. The presented assembly design of permanent magnetic rings with iron modules can produce a higher-order flat shape axial magnetic field profile for a higher-order frequency range with an increase in the remanence value for each magnetic arc.

5. The proposed iron modules design with permanent magnetic ring assemblies can produce more long-range axial magnetic field profiles for higher-order outer radius magnetic arc structure assemblies.

6. The iron module used in the extraction side has reduced the excessive magnetic field, commonly known as the fringe field. Due to the reduction in the magnetic fringe area, the current design can reduce the possibility of sparking during extraction and the possibility of ion beam deflection during the trajectory of the ion beam.

7. The first invented iron module setup is located within ridge steps adjacent to rectangular microwave windows. Therefore, it will not cause any problem for the impedance matching process during microwave coupling.

8. A flat-shaped axial ECR region is formed from the injection site to the extraction site so the ECR can ignite a long-distance uniform plasma inside the plasma cavity.

9. The large volume production of uniform ECR plasma can be used for surface treatment, plasma exposure for materials, Etching process.