Physics Design Of Heavy-ion Microporous Membrane Irradiation Beam Line On HI-13Tandem Accelerator

Polymer films were irradiated by accelerator heavy-ion beam and carried out bychemical etching processing, then microfiltration membranes, a kind of nuclear trackmembranes were obtained. The pores are sieve pore, approximate cylindrical, roundand uniform. Pore size and density can be strictly controlled according to need. It is akind of excellent properties and has many advantages as large filter rate, excellentmechanical properties and good thermal stability, which has widely prospects forapplication in medical and biological agents, electronic industry, food industry,environmental science, materials science and other fields.HI-13tandem accelerator is the largest electrostatic accelerator in China, whichcan provide many kinds of ion, the ion energy is high enough and can be adjustedcontinuously. Polyester membranes were irradiated by heavy ion produced by HI-13tandem accelerator to develop microporous membrane at CIAE, the microporeuniformity is determined by beam intensity distribution, improve the uniformity ofmicropore is the key of product quality for heavy ion microporous membrane.According to the production requirements of irradiation uniformity is better than90%, this paper is designed two kinds of irradiation scheme; For one is the Lissajousscanning method with electromagnetic field, Lissajous scanning method is pressurebeam for periodic force with different frequency on the X and Y direction, the beamwill scanning along with the specific Lissajous graph, the beam intensity distributionon the target will become uniform in scanning period which by choosing suitablefrequency and the beam spot size to achievement. When the target is stationary, theLissajous scanning is very easy to get an uniform beam distribution; when the targetmoves at a certain speed, this equivalent to the target is stationary and beam in thescanning at the same time is always move in one direction which can damage theuniformity for trajectory of the beam, meanwhile,the beam intensity distribution willbecome damage also. In this paper, through analyzed of the relationship between the beam spot size, intensity distribution and scanning frequency, meanwhile, theintensity distribution of beam on target is calculated and the optical parameters isdesigned also, which can obtained the uniformity by irradiation is better than90%onthe theory. But this irradiation uniformity is the dynamic distribution, so it has veryhigh stability requirements for the equipment, and has less control means onuniformity.For another one is the correction with octupole magnet, this method is use ofoctupole magnet on the effect of high order phase difference to correct beamdistribution from Gauss distribution to uniform distribution in approximately whichcan greatly improve the beam uniformity; The irradiation uniformity is the staticdistribution, and pore density is determined by the transmission speed of membrane.This paper analyzed the principle of octupole magnet, designed the optical parametersof beam line, and simulated the beam distribution after corrected, the results showedthat the irradiation uniformity and beam utilization rate can reach90%. But suchirradiation method requirements are very strict for installation alignment tolerance ofoptics element on the beam line, the displacement tolerance should be controlledwithin0.2mm and rotation tolerance should be controlled within0.5mrad, meanwhile,alignment tolerance will cause the beam utilization rate declined; Therefore, in orderto overcome the influence on the beam uniformity with installation and alignmenttolerance, this paper puts forward the steer magnet to tuning beam. At the end of thispaper, the physical design of the octupole magnet is given, it includes good fieldregion through the beam optics calculation, analyzed the magnetic pole shape,calculated the magnetic pole width and the results show that the distribution ofmagnetic field can reach the design requirements. At last, the excitation coil and theexcitation power is calculated, in the light of conductor, the water-cooled model isdesigned and water parameters is calculated.This study provides a practical and feasible way to industrial production ofheavy-ion microporous membrane.