Short answer is, you can't. A Response.Redirect simply changes the destination of a URL, and has nothing to do with browser windows. You need to either make the initial link to the page from which you are redirecting open in a new window (via target= attribute or script), or make the page to which you have redirected have some script which spawns a new window.
All of these solutions, except an <a> tag with a target= (which doesn't help you if you're having postback involved), require script. And I imagine you knew about <a target=...> already anyway.
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