How to programatically authenticate user to Active Directory to get SharePoint 2013 Windows Claim

Hi.

The problem: 

See code below;

the ensureuser command is working fine, in the sense that the user will actually have the correct right in SharePoint as a valid user which can log on (as far as I have inspected the access tables in SharePoint's sql database).

But after the "web.Update();" statement, which statements will autenticate user with AD programmatically, so that the user will be logged in to SharePoint with a SharePoint windows claim?

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SPSecurity.RunWithElevatedPrivileges(() =>
            {
                {
                    using (SPSite site = SPContext.Current.Site)
                    {
                        using (SPWeb web = site.OpenWeb())
                        {
                            web.AllowUnsafeUpdates = true;
                            web.EnsureUser(String.Format("{0}\\{1}", domainName, accountName));
                            web.Update();
                        }
                    }
                }
            });
-----------------
Background information (not important):
Because of integration with the Microsoft BI-stack's OLAP cubes, our implementation require that I create users from external logon provider into local Active Directory, and then authenticate Sharepoint to this newly created account in order to get a Windows claim. (The process needs to run aa an unautehenticated user up until authorization With AD.)
When the user access reports as an authenticated user, the cube logic need a Windows Principal attached in order to have the  cube's internal security dimension working, and here the Claims to Windows Token service (c2WTS) will intercept and attach this by a lookup to Active Directory using the UPN in the Claim.
Best regards