Put the chopped rhubarb, water, sugar, orange zest, ginger, and salt into a 3 to 4-quart pot. Heat on high heat to bring to a boil. Lower the heat to low to simmer, covered, for 5 minutes, or until the sugar has dissolved and the rhubarb is falling apart tender. Remove from heat and let cool for 10 minutes. Either use an immersion blender or work in batches with a standing blender to purée the mixture until smooth. Press the mixture through a fine mesh sieve to remove any of the stringy pulp. Stir in the corn syrup. Cover and refrigerate until totally chilled, several hours or overnight. (Can more quickly chill in the freezer if you check it and stir it every 15 minutes.) Process in your ice cream maker according to the manufacturer’s instructions.